Light-emitting element, compound, organic compound, display module, lighting module, light-emitting device, display device, lighting device, and electronic device

ABSTRACT

A light-emitting element having high emission efficiency is provided. A light-emitting element having a low driving voltage is provided. A novel compound which can be used for a transport layer or as a host material or a light-emitting material of a light-emitting element is provided. A novel compound with a benzofuropyrimidine skeleton is provided. Also provided is a light-emitting element which includes the compound with the benzofuropyrimidine skeleton between a pair of electrodes.

This application is a continuation of U.S. application Ser. No.16/255,312, filed on Jan. 23, 2019 which a continuation of U.S.application Ser. No. 15/890,899, filed on Feb. 7, 2018 (now U.S. Pat.No. 10,193,086 issued Jan. 29, 2019) which is a continuation of U.S.application Ser. No. 14/224,641, filed on Mar. 25, 2014 (now U.S. Pat.No. 9,905,872 issued Feb. 27, 2018) which are all incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a light-emitting element, a compound,an organic compound, a display module, a lighting module, alight-emitting device, a display device, a lighting device, and anelectronic device.

BACKGROUND ART

As next generation lighting devices or display devices, display devicesusing light-emitting elements (organic EL elements) in which organiccompounds are used for light-emitting substances have been developedrapidly because of their advantages of thinness, lightweightness, highspeed response to input signals, low power consumption, and the like.

In an organic EL element, voltage application between electrodes betweenwhich a light-emitting layer is provided causes recombination ofelectrons and holes injected from the electrodes, which brings alight-emitting substance into an excited state, and the return from theexcited state to the ground state is accompanied by light emission.Since the wavelength of light emitted from a light-emitting substance ispeculiar to the light-emitting substance, use of different types oforganic compounds for light-emitting substances makes it possible toprovide light-emitting elements which exhibit various wavelengths.

In the case of display devices which are expected to display images,such as displays, at least three-color light, i.e., red light, greenlight, and blue light are necessary for reproduction of full-colorimages. Further, in lighting devices, light having wavelength componentsevenly spreading in the visible light region is ideal for achieving ahigh color rendering property, but actually, light obtained by mixingtwo or more kinds of light having different wavelengths is often usedfor lighting application. Note that it is known that mixing light ofthree colors of red, green, and blue allows generation of white lighthaving a high color rendering property.

Light emitted from a light-emitting substance is peculiar to thesubstance as described above. However, important performances as alight-emitting element, such as a lifetime, power consumption, andemission efficiency, are not only dependent on the light-emittingsubstance but also greatly dependent on layers other than thelight-emitting layer, an element structure, properties of alight-emitting substance and a host material, compatibility betweenthem, carrier balance, and the like. Therefore, there is no doubt thatmany kinds of light-emitting element materials are necessary for agrowth in this field. For the above-described reasons, light-emittingelement materials with a variety of molecular structures have beenproposed (e.g., see Patent Document 1).

As is generally known, the generation ratio of a singlet excited stateto a triplet excited state in a light-emitting element usingelectroluminescence is 1:3. Therefore, a light-emitting element in whicha phosphorescent material capable of converting the triplet excitedenergy to light emission is used as a light-emitting material cantheoretically realize higher emission efficiency than a light-emittingelement in which a fluorescent material capable of converting thesinglet excited energy to light emission is used as a light-emittingmaterial.

As a host material in a host-guest type light-emitting layer or asubstance contained in each carrier-transport layer in contact with alight-emitting layer, a substance having a wider band gap or a highertriplet excitation level (a larger energy difference between a tripletexcited state and a singlet ground state) than a light-emittingsubstance is used for efficient conversion of excitation energy intolight emission from the light-emitting substance.

However, most of substances used as host materials in the light-emittingelements are fluorescent, and the triplet excited state of the substanceis at a lower energy level than the singlet excited state thereof.Therefore, a host material needs to have a wider band gap in the casewhere a phosphorescent material is used as a light-emitting materialthan in the case where a fluorescent material is used as alight-emitting material even when the phosphorescent material and thefluorescent material have the same emission wavelength.

Accordingly, to efficiently obtain phosphorescence having a shorterwavelength, a host material and a carrier-transport material each havingan extremely wide band gap are necessary. However, it is difficult todevelop a substance to be a light-emitting element material which hassuch a wide band gap while enabling a balance between importantcharacteristics of a light-emitting element, such as low driving voltageand high emission efficiency.

REFERENCE Patent Document

-   [Patent Document 1] Japanese Published Patent Application No.    2007-15933

DISCLOSURE OF INVENTION

In view of the above, an object of one embodiment of the presentinvention is to provide a light-emitting element having high emissionefficiency. An object of one embodiment of the present invention is toprovide a light-emitting element having a low driving voltage. An objectof one embodiment of the present invention is to provide alight-emitting element emitting phosphorescence with high emissionefficiency. An object of one embodiment of the present invention is toprovide a light-emitting element emitting green to blue phosphorescencewith high emission efficiency.

An object of one embodiment of the present invention is to provide anovel compound which can be used for a carrier-transport layer or as ahost material or a light-emitting material of a light-emitting element.Specifically, an object of one embodiment of the present invention is toprovide a novel compound which makes it possible to obtain alight-emitting element having good characteristics when used in alight-emitting element emitting phosphorescence with a wavelengthshorter than that of green.

An object of one embodiment of the present invention is to provide aheterocyclic compound which has a high triplet excitation level (T₁level). Specifically, an object of one embodiment of the presentinvention is to provide a heterocyclic compound which makes it possibleto obtain a light-emitting element having high emission efficiency whenused in a light-emitting element emitting phosphorescence with awavelength shorter than that of green.

An object of one embodiment of the present invention is to provide aheterocyclic compound which has a high carrier-transport property.Specifically, an object of one embodiment of the present invention is toprovide a heterocyclic compound which can be used in a light-emittingelement emitting phosphorescence with a wavelength shorter than that ofgreen and allows the driving voltage of the light-emitting element to below.

An object of one embodiment of the present invention is to provide alight-emitting element using the heterocyclic compound.

An object of one embodiment of the present invention is to provide adisplay module, a lighting module, a light-emitting device, a lightingdevice, a display device, and an electronic device each using theheterocyclic compound and achieving low power consumption.

Note that the descriptions of these objects do not disturb the existenceof other objects. All the objects do not necessarily need to be achievedsimultaneously in one embodiment of the present invention. Other objectsmay be apparent from the description of the specification, the drawings,the claims, and the like.

Any of the above objects can be achieved by a compound having abenzofuropyrimidine skeleton and application of the compound to alight-emitting element.

One embodiment of the present invention is a compound represented byGeneral Formula (G1).

In General Formula (G1), A¹ represents any one of a substituted orunsubstituted aryl group having 6 to 100 carbon atoms, a substituted orunsubstituted heteroaryl group, and a group having 6 to 100 carbon atomsand including a substituted or unsubstituted aryl group and asubstituted or unsubstituted heteroaryl group. R¹ to R⁵ separatelyrepresent any one of hydrogen, an alkyl group having 1 to 6 carbonatoms, a substituted or unsubstituted monocyclic saturated hydrocarbonhaving 5 to 7 carbon atoms, a substituted or unsubstituted polycyclicsaturated hydrocarbon having 7 to 10 carbon atoms, and a substituted orunsubstituted aryl group having 6 to 13 carbon atoms.

Another embodiment of the present invention is a compound represented byGeneral Formula (G2).

In General Formula (G2), R¹ to R⁵ separately represent any one ofhydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted orunsubstituted monocyclic saturated hydrocarbon having 5 to 7 carbonatoms, a substituted or unsubstituted polycyclic saturated hydrocarbonhaving 7 to 10 carbon atoms, and a substituted or unsubstituted arylgroup having 6 to 13 carbon atoms. Further, α represents a substitutedor unsubstituted phenylene group and n is an integer from 0 to 4.Ht_(uni) represents a hole-transport skeleton.

A further embodiment of the present invention is the above compound inwhich n is 2.

A still further embodiment of the present invention is a compoundrepresented by General Formula (G3).

In General Formula (G3), R¹ to R⁵ separately represent any one ofhydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted orunsubstituted monocyclic saturated hydrocarbon having 5 to 7 carbonatoms, a substituted or unsubstituted polycyclic saturated hydrocarbonhaving 7 to 10 carbon atoms, and a substituted or unsubstituted arylgroup having 6 to 13 carbon atoms. Ht_(uni) represents a hole-transportskeleton.

A yet still further embodiment of the present invention is any of theabove compounds in which Ht_(uni) represents any one of a substituted orunsubstituted dibenzothiophenyl group, a substituted or unsubstituteddibenzofuranyl group, and a substituted or unsubstituted carbazolylgroup.

A yet still further embodiment of the present invention is any of theabove compounds in which Ht_(uni) is any one of groups represented byGeneral Formulae (Ht-1) to (Ht-6).

In General Formula 4, R⁶ to R¹⁵ separately represent any one ofhydrogen, an alkyl group having 1 to 6 carbon atoms, and a substitutedor unsubstituted phenyl group. R¹⁶ represents any one of an alkyl grouphaving 1 to 6 carbon atoms and a substituted or unsubstituted phenylgroup.

A yet still further embodiment of the present invention is any of theabove compounds in which the substituted or unsubstituted aryl grouprepresented by A¹ or the group including a substituted or unsubstitutedaryl group and a substituted or unsubstituted heteroaryl group andrepresented by A¹ has 6 to 54 carbon atoms.

A yet still further embodiment of the present invention is any of theabove compounds in which the substituted or unsubstituted aryl grouprepresented by A¹ or the group including a substituted or unsubstitutedaryl group and a substituted or unsubstituted heteroaryl group andrepresented by A¹ has 6 to 33 carbon atoms.

A yet still further embodiment of the present invention is any of theabove compounds in which R⁶ to R¹⁵ each represent hydrogen.

A yet still further embodiment of the present invention is any of theabove compounds in which R² and R⁴ each represent hydrogen.

A yet still further embodiment of the present invention is any of theabove compounds in which R¹ to R⁵ each represent hydrogen.

A yet still further embodiment of the present invention is any of theabove compounds in which R², R⁴, and R⁶ to R¹⁵ each represent hydrogen.

A yet still further embodiment of the present invention is any of theabove compounds in which R¹ to R¹⁵ each represent hydrogen.

A yet still further embodiment of the present invention is a compoundrepresented by Structural Formula (100).

A yet still further embodiment of the present invention is a compoundrepresented by Structural Formula (200).

A yet still further embodiment of the present invention is a compoundrepresented by Structural Formula (300).

A yet still further embodiment of the present invention is a compoundrepresented by Structural Formula (115).

It is preferable that the compound of one embodiment of the presentinvention be used as a host material in a light-emitting layer or amaterial of a carrier-transport layer.

A yet still further embodiment of the present invention is a compoundwhich includes any of the above compounds as a partial structure.

Specifically, the yet still further embodiment of the present inventionis an organometallic complex which includes any of the above compoundsas a ligand.

A yet still further embodiment of the present invention is alight-emitting element that includes a compound with abenzofuropyrimidine skeleton between a pair of electrodes.

A yet still further embodiment of the present invention is alight-emitting element that includes a light-emitting layer between apair of electrodes. The light-emitting layer contains at least alight-emitting substance and a compound with a benzofuropyrimidineskeleton.

A yet still further embodiment of the present invention is alight-emitting element that includes a light-emitting layer between apair of electrodes. The light-emitting layer contains an iridium complexand a compound with a benzofuropyrimidine skeleton.

A yet still further embodiment of the present invention is alight-emitting element that includes a carrier-transport layer,specifically, an electron-transport layer between a pair of electrodes.The electron-transport layer contains a compound with abenzofuropyrimidine skeleton.

A yet still further embodiment of the present invention is alight-emitting element that includes a light-emitting layer and anelectron-transport layer between a pair of electrodes. At least one ofthe light-emitting layer and the electron-transport layer contains acompound with a benzofuropyrimidine skeleton.

A yet still further embodiment of the present invention is the abovelight-emitting element in which the benzofuropyrimidine skeleton is abenzofuro[3,2-d]pyrimidine skeleton.

Typical examples of the above compound with a benzofuro[3,2-d]pyrimidineskeleton are already described above.

A yet still further embodiment of the present invention is a displaymodule including the above light-emitting element.

A yet still further embodiment of the present invention is a lightingmodule including the above light-emitting element.

A yet still further embodiment of the present invention is alight-emitting device including the above light-emitting element and aunit for controlling the light-emitting element.

A yet still further embodiment of the present invention is a displaydevice including the above light-emitting element in a display portionand a unit for controlling the light-emitting element.

A yet still further embodiment of the present invention is a lightingdevice including the above light-emitting element in a lighting portionand a unit for controlling the light-emitting element.

A yet still further embodiment of the present invention is an electronicdevice including the above light-emitting element.

The emission efficiency of the light-emitting element of one embodimentof the present invention is high. Driving voltage of the light-emittingelement is low. The light-emitting element exhibits light emission ingreen to blue regions with high emission efficiency.

The heterocyclic compound of one embodiment of the present invention hasa wide energy gap. Further, the heterocyclic compound has a highcarrier-transport property. Accordingly, the heterocyclic compound canbe suitably used in a light-emitting element, as a material of acarrier-transport layer, a host material in a light-emitting layer, or alight-emitting substance in the light-emitting layer.

One embodiment of the present invention can provide a display module, alighting module, a light-emitting device, a lighting device, a displaydevice, and an electronic device each using the heterocyclic compoundand achieving low power consumption.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are schematic diagrams of light-emitting elements.

FIG. 2 is a schematic diagram of an organic semiconductor element.

FIGS. 3A and 3B are schematic diagrams of an active matrixlight-emitting device.

FIGS. 4A and 4B are schematic diagrams of active matrix light-emittingdevices.

FIG. 5 is a schematic diagram of an active matrix light-emitting device.

FIGS. 6A and 6B are schematic diagrams of a passive matrixlight-emitting device.

FIGS. 7A to 7D illustrate electronic devices.

FIG. 8 illustrates a light source device.

FIG. 9 illustrates a lighting device.

FIG. 10 illustrates a lighting device and an electronic device.

FIG. 11 illustrates in-vehicle display devices and lighting devices.

FIGS. 12A to 12C illustrate an electronic device.

FIGS. 13A and 13B are NMR charts of 4mDBTBPBfpm-II.

FIGS. 14A and 14B show an absorption spectrum and an emission spectrumof 4mDBTBPBfpm-II.

FIGS. 15A and 15B show results of LC/MS analysis of 4mDBTBPBfpm-II.

FIGS. 16A and 16B are NMR charts of 4mCzBPBfpm.

FIGS. 17A and 17B show an absorption spectrum and an emission spectrumof 4mCzBPBfpm.

FIGS. 18A and 18B show results of LC/MS analysis of 4mCzBPBfpm.

FIG. 19 shows current density-luminance characteristics of alight-emitting element 1.

FIG. 20 shows voltage-luminance characteristics of a light-emittingelement 1.

FIG. 21 shows luminance-current efficiency characteristics of alight-emitting element 1.

FIG. 22 shows luminance-external quantum efficiency characteristics of alight-emitting element 1.

FIG. 23 shows luminance-power efficiency characteristics of alight-emitting element 1.

FIG. 24 shows an emission spectrum of a light-emitting element 1.

FIG. 25 shows time dependence of normalized luminance of alight-emitting element 1.

FIG. 26 shows current density-luminance characteristics of alight-emitting element 2.

FIG. 27 shows voltage-luminance characteristics of a light-emittingelement 2.

FIG. 28 shows luminance-current efficiency characteristics of alight-emitting element 2.

FIG. 29 shows luminance-external quantum efficiency characteristics of alight-emitting element 2.

FIG. 30 shows luminance-power efficiency characteristics of alight-emitting element 2.

FIG. 31 shows an emission spectrum of a light-emitting element 2.

FIG. 32 shows time dependence of normalized luminance of alight-emitting element 2.

FIG. 33 shows current density-luminance characteristics of alight-emitting element 3.

FIG. 34 shows voltage-luminance characteristics of a light-emittingelement 3.

FIG. 35 shows luminance-current efficiency characteristics of alight-emitting element 3.

FIG. 36 shows luminance-external quantum efficiency characteristics of alight-emitting element 3.

FIG. 37 shows luminance-power efficiency characteristics of alight-emitting element 3.

FIG. 38 shows an emission spectrum of a light-emitting element 3.

FIG. 39 shows time dependence of normalized luminance of alight-emitting element 3.

FIGS. 40A and 40B are NMR charts of 4mFDBtPBfpm.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described. Itis easily understood by those skilled in the art that modes and detailsdisclosed herein can be modified in various ways without departing fromthe spirit and scope of the present invention. Therefore, the presentinvention is not construed as being limited to description of theembodiments.

Embodiment 1

A compound of one embodiment of the present invention which is describedin this embodiment is a compound with a benzofuropyrimidine skeleton. Acompound with the skeleton excels at transporting carriers (particularlyelectrons). Owing to this, a light-emitting element with low drivingvoltage can be provided.

The compound can have a high triplet excitation level (T₁ level) andthus can be suitably applied to a light-emitting element that uses aphosphorescent substance. Specifically, the high triplet excitationlevel (T₁ level) of the compound can inhibit transfer of excitationenergy of the phosphorescent substance to the compound, which leads toefficient conversion of excitation energy into light emission. A typicalexample of the phosphorescent substance is an iridium complex.

Note that a specific example of the benzofuropyrimidine skeleton is, butnot limited to, a benzofuro[3,2-d]pyrimidine skeleton.

A preferable example of the compound with a benzofuropyrimidine skeletonis represented by General Formula (G1).

In the formula, A¹ represents any one of a substituted or unsubstitutedaryl group having 6 to 100 carbon atoms, a substituted or unsubstitutedheteroaryl group, and a group having 6 to 100 carbon atoms and includinga substituted or unsubstituted aryl group and a substituted orunsubstituted heteroaryl group.

Typical examples of the aryl group having 6 to 100 carbon atoms includegroups represented by General Formulae (A¹-1) to (A¹-6). Note that thegroups shown below are merely typical examples and the aryl group having6 to 100 carbon atoms are not limited to these examples.

In the formulae, R^(A1) to R^(A6) each have 1 to 4 substituents, and thesubstituents are separately any one of hydrogen, an alkyl group having 1to 6 carbon atoms, a substituted or unsubstituted monocyclic saturatedhydrocarbon having 5 to 7 carbon atoms, a substituted or unsubstitutedpolycyclic saturated hydrocarbon having 7 to 10 carbon atoms, and asubstituted or unsubstituted aryl group having 6 to 13 carbon atoms.

Further, typical examples of the heteroaryl group or the group includingthe aryl group and the heteroaryl group include groups represented byGeneral Formulae (A¹-10) to (A¹-25). Note that the groups shown beloware merely typical examples and A¹ is not limited to these examples.

Further, R¹ to R⁵ separately represent any one of hydrogen, an alkylgroup having 1 to 6 carbon atoms, a substituted or unsubstitutedmonocyclic saturated hydrocarbon having 5 to 7 carbon atoms, asubstituted or unsubstituted polycyclic saturated hydrocarbon having 7to 10 carbon atoms, and a substituted or unsubstituted aryl group having6 to 13 carbon atoms.

Note that specific examples of the alkyl group having 1 to 6 carbonatoms, which is represented by R¹ to R⁵, include a methyl group, anethyl group, a propyl group, an isopropyl group, a butyl group, asec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group,an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentylgroup, a hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexylgroup, a neohexyl group, a 3-methylpentyl group, a 2-methylpentyl group,a 2-ethylbutyl group, a 1,2-dimethylbutyl group, and a 2,3-dimethylbutylgroup. Specific examples of the substituted or unsubstituted monocyclicsaturated hydrocarbon having 5 to 7 carbon atoms, which is representedby R¹ to R⁵, include a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cyclooctyl group, a2-methylcyclohexyl group, and a 2,6-dimethylcyclohexyl group. Specificexamples of the substituted or unsubstituted polycyclic saturatedhydrocarbon having 7 to 10 carbon atoms, which is represented by R¹ toR⁵, include a decahydronaphthyl group and an adamantyl group. Specificexamples of the substituted or unsubstituted aryl group having 6 to 13carbon atoms, which is represented by R¹ to R⁵, include a phenyl group,an o-tolyl group, a m-tolyl group, a p-tolyl group, a mesityl group, ano-biphenyl group, a m-biphenyl group, a p-biphenyl group, a 1-naphthylgroup, a 2-naphthyl group, a fluorenyl group, and a9,9-dimethylfluorenyl group.

R¹ to R⁵ each may have a substituent as long as the substituent is agroup that does not significantly change the characteristics of thecompound, such as an alkyl group having 1 to 3 carbon atoms.

A further preferable example of benzofuropyrimidine described in thisembodiment can be represented by General Formula (G2).

R¹ to R⁵ in General Formula (G2) are similar to those in General Formula(G1) and thus redundant description is omitted. Refer to the descriptionof R¹ to R⁵ in General Formula (G1).

In General formula (G2), c represents a substituted or unsubstitutedphenylene group, and n is an integer from 0 to 4. α may have asubstituent as long as the substituent is a group that does notsignificantly change the characteristics of the compound, such as analkyl group having 1 to 3 carbon atoms.

To inhibit interaction between Ht_(uni) and the benzofuropyrimidineskeleton and keep a high triplet excitation level (T₁ level), n ispreferably 1 or more; to improve a thermophysical property and stabilityof a molecule, n is preferably 2. Further, when n is 2, the divalentgroup denoted by a and n is preferably a 1,1′-biphenyl-3,3′-diyl group.

In General Formula (G2), Ht_(uni) represents a hole-transport skeleton.To keep a high triplet excitation level (T₁ level), Ht_(uni) ispreferably a substituted or unsubstituted dibenzothiophenyl group, asubstituted or unsubstituted dibenzofuranyl group, or a substituted orunsubstituted carbazolyl group. The group represented by Ht_(uni) mayhave a substituent as long as the substituent is a group that does notsignificantly change the characteristics of the compound, such as analkyl group having 1 to 3 carbon atoms.

Among specific examples of Ht_(uni), groups represented by GeneralFormulae (Ht-1) to (Ht-6) are preferable because they can be easilysynthesized. Needless to say, Ht_(uni) is not limited to the examplesshown below.

R⁶ to R¹⁵ separately represent any one of hydrogen, an alkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted phenylgroup. In addition, R¹⁶ represents any one of an alkyl group having 1 to6 carbon atoms and a substituted or unsubstituted phenyl group. Thegroups represented by R⁶ to R¹⁵ and R¹⁶ each may have a substituent aslong as the substituent is a group that does not significantly changethe characteristics of the compound, such as an alkyl group having 1 to3 carbon atoms.

The compound of one embodiment of the present invention in whichHt_(uni) is any one of the groups represented by General Formulae (Ht-1)to (Ht-6) is preferable because the compound has a high tripletexcitation level (T₁ level) and a hole-transport property. The groupsrepresented by General Formulae (Ht-1) to (Ht-6) each serve as anelectron donor site when combined with a benzofuropyrimidine skeleton(benzofuropyrimidine serves as an electron acceptor site). Therefore, inview of an electric charge transport property of a film, the compound ofone embodiment of the present invention in which Ht_(uni) is any one ofthe groups represented by General Formulae (Ht-1) to (Ht-6) ispreferably used as a material of a light-emitting element because thecompound has a high conductive property in its bulk and a highcarrier-injection property at its interface, which enables low-voltagedriving.

It is preferable that R⁶ to R¹⁵ in the groups represented by GeneralFormulae (Ht-1) to (Ht-6) be each hydrogen, in which case widelyavailable raw materials can be used and the compound can be easilysynthesized.

To obtain similar advantages, both R² and R⁴ in the compound representedby General Formula (G2) preferably represent hydrogen. It is furtherpreferable that R¹ to R⁵ each represent hydrogen.

Typical examples of the above-described compound are shown below. Notethat the compounds described in this embodiment are not limited to theexamples shown below.

The above-described compound of one embodiment of the present inventionhas an excellent carrier-transport property and thus is suitable for acarrier-transport material or a host material. Owing to this, alight-emitting element driven at low voltage can also be provided. Inaddition, the compound of one embodiment of the present invention canhave a high triplet excitation level (T₁ level), which makes it possibleto provide a phosphorescent light-emitting element with high emissionefficiency. Specifically, the compound can provide high emissionefficiency even to a phosphorescent light-emitting element that has anemission peak on a shorter wavelength side than green. Moreover, thehigh triplet excitation level (T₁ level) means that the compound has awide band gap, which allows a blue-emissive fluorescent light-emittingelement to efficiently emit light.

Next, a method for synthesizing the compound represented by GeneralFormula (G1) is described.

The compound represented by General Formula (G1) can be synthesized by asimple synthesis scheme as follows. For example, as shown in SynthesisScheme (a), the compound can be synthesized by causing a reactionbetween a halide (A1) of a benzofuropyrimidine derivative and a boronicacid compound (A2) of an aryl group, a heteroaryl group, or a groupincluding an aryl group and a heteroaryl group which is represented byA¹. In the formula, X represents a halogen element. B represents aboronic acid, a boronic ester, a cyclic-triolborate salt, or the like.As the cyclic-triolborate salt, a lithium salt, a potassium salt, or asodium salt may be used.

Note that in Synthesis Scheme (a), R¹ to R⁵ separately represent any oneof hydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted orunsubstituted monocyclic saturated hydrocarbon having 5 to 7 carbonatoms, a substituted or unsubstituted polycyclic saturated hydrocarbonhaving 7 to 10 carbon atoms, and a substituted or unsubstituted arylgroup having 6 to 13 carbon atoms.

Note that it is also possible to cause a reaction between a boronic acidcompound of a benzofuropyrimidine derivative and a halide of A¹.

A variety of the above compounds (A1) and (A2) can be synthesized, whichmeans that a variety of the compound represented by General Formula (G1)can be synthesized. Thus, a feature of the compound of one embodiment ofthe present invention is the abundance of variations.

The above is the description of the example of a method for synthesizingthe compound of one embodiment of the present invention; however, thepresent invention is not limited thereto and any other synthesis methodmay be employed.

A compound that includes the compound described in this embodiment as apartial structure is also one embodiment of the present invention. As anexample of such a compound, an organometallic complex that includes theabove structure as a ligand can be given.

That is, the compound includes the compound with the benzofuropyrimidineskeleton as a partial structure, and the partial structure isrepresented by General Formula (G1).

In General Formula (G1), R¹ to R⁵ are similar to those described aboveand thus redundant description is omitted.

In General Formula (G1), A¹ represents any one of a substituted orunsubstituted aryl group having 6 to 100 carbon atoms, a substituted orunsubstituted heteroaryl group, and a group having 6 to 100 carbon atomsand including a substituted or unsubstituted aryl group and asubstituted or unsubstituted heteroaryl group. Specific examples of agroup that can be used as A¹ are already described above and thusredundant description is omitted.

Note that when the above compound including the partial structurerepresented by General Formula (G1) is an organometallic complex and itscentral metal is iridium or platinum, this compound can also be used asa phosphorescent substance.

Embodiment 2

This embodiment will show an example in which the compound representedby General Formula (G1) in Embodiment 1 is used for an active layer of avertical transistor (static induction transistor (SIT)), which is a kindof an organic semiconductor element.

The element has a structure in which a thin-film active layer 1202containing the compound represented by General Formula (G1) is providedbetween a source electrode 1201 and a drain electrode 1203, and gateelectrodes 1204 are embedded in the active layer 1202, as illustrated inFIG. 2 . The gate electrodes 1204 are electrically connected to a unitfor applying gate voltage, and the source electrode 1201 and the drainelectrode 1203 are electrically connected to a unit for controlling thevoltage between the source and the drain.

In such an element structure, when voltage is applied between the sourceand the drain under the condition where gate voltage is not applied,current flows (on state). Then, by application of voltage to the gateelectrode in that state, a depletion layer is formed in the periphery ofthe gate electrode 1204, and the current ceases flowing (off state).With such a mechanism, the element operates as a transistor.

Like a light-emitting element, a vertical transistor should contain amaterial that can achieve both a high carrier-transport property andhigh film quality for an active layer; the compound represented byGeneral Formula (G1) meets such a requirement and therefore can besuitably used.

Embodiment 3

In this embodiment, one embodiment of a light-emitting element thatincludes a compound with a benzofuropyrimidine skeleton will bedescribed with reference to FIG. 1A.

The light-emitting element of this embodiment has a plurality of layersbetween a pair of electrodes. In this embodiment, the light-emittingelement includes a first electrode 101, a second electrode 102, and anEL layer 103 provided between the first electrode 101 and the secondelectrode 102. Note that in FIG. 1A, the first electrode 101 functionsas an anode and the second electrode 102 functions as a cathode. Inother words, when a voltage is applied between the first electrode 101and the second electrode 102 such that the potential of the firstelectrode 101 is higher than that of the second electrode 102, lightemission is obtained. Of course, a structure in which the firstelectrode functions as a cathode and the second electrode functions asan anode can be employed. In that case, the stacking order of layers inthe EL layer is reversed from the stacking order described below. Notethat in the light-emitting element of this embodiment, at least one oflayers in the EL layer 103 contains the compound with abenzofuropyrimidine skeleton. Note that a layer that contains thecompound with a benzofuropyrimidine skeleton is preferably alight-emitting layer or an electron-transport layer because thecharacteristics of the compound can be utilized and a light-emittingelement having favorable characteristics can be obtained.

For the electrode functioning as an anode, any of metals, alloys,electrically conductive compounds, and mixtures thereof which have ahigh work function (specifically, a work function of 4.0 eV or more) orthe like is preferably used. Specific examples are indium oxide-tinoxide (ITO: indium tin oxide), indium oxide-tin oxide containing siliconor silicon oxide, indium oxide-zinc oxide, indium oxide containingtungsten oxide and zinc oxide (IWZO), and the like. Films of theseelectrically conductive metal oxides are usually formed by sputteringbut may be formed by a sol-gel method or the like. For example, indiumoxide-zinc oxide can be formed by a sputtering method using a target inwhich zinc oxide is added to indium oxide at higher than or equal to 1wt % and lower than or equal to 20 wt %. Moreover, indium oxidecontaining tungsten oxide and zinc oxide (IWZO) can be formed by asputtering method using a target in which tungsten oxide is added toindium oxide at higher than or equal to 0.5 wt % and lower than or equalto 5 wt % and zinc oxide is added to indium oxide at higher than orequal to 0.1 wt % and lower than or equal to 1 wt %. Other examples aregold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr),molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), anitride of a metal material (such as titanium nitride), and the like.Graphene may also be used.

There is no particular limitation on the stacked structure of the ELlayer 103. The EL layer 103 can be formed by combining a layercontaining a substance having a high electron-transport property, alayer containing a substance having a high hole-transport property, alayer containing a substance having a high electron-injection property,a layer containing a substance having a high hole-injection property, alayer containing a bipolar substance (a substance having a highelectron-transport and hole-transport property), a layer having acarrier-blocking property, and the like as appropriate. In thisembodiment, the EL layer 103 has a structure in which a hole-injectionlayer 111, a hole-transport layer 112, a light-emitting layer 113, anelectron-transport layer 114, and an electron-injection layer 115 arestacked in this order over the electrode functioning as an anode.Materials contained in the layers are specifically given below.

The hole-injection layer 111 is a layer containing a substance having ahole-injection property. The hole-injection layer 111 can be formedusing molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide,manganese oxide, or the like. The hole-injection layer 111 can also beformed using a phthalocyanine-based compound such as phthalocyanine(abbreviation: H₂Pc) or copper phthalocyanine (abbreviation: CuPc); anaromatic amine compound such as4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl(abbreviation:DPAB) orN,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD); a high molecule compound such aspoly(ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS), orthe like.

The hole-injection layer 111 can be formed using a composite material inwhich a substance exhibiting an electron-accepting property(hereinafter, simply referred to as “electron-accepting substance”) withrespect to a substance having a hole-transport property is contained inthe substance having a hole-transport property. In this specification,the composite material refers to not a material in which two materialsare simply mixed but a material in the state where charge transferbetween the materials can be caused by a mixture of a plurality ofmaterials. This charge transfer includes the charge transfer that occursonly when an electric field exists.

Note that by using the composite material in which theelectron-accepting substance is contained in the substance having ahole-transport property, a material used for forming the electrode canbe selected regardless of the work function of the material. In otherwords, besides a material having a high work function, a material havinga low work function can be used for the electrode functioning as ananode. Examples of the electron-accepting substance are7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and the like. A transition metal oxide can also beused. In particular, an oxide of a metal belonging to any of Groups 4 to8 of the periodic table can be suitably used. Specifically, vanadiumoxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide,tungsten oxide, manganese oxide, and rhenium oxide are preferablebecause of their high electron-accepting properties. Among these,molybdenum oxide is especially preferable as the electron-acceptingsubstance because it is stable in the air, has a low hygroscopicproperty, and is easily handled.

As the substance with a hole-transport property used for the compositematerial, any of a variety of organic compounds such as an aromaticamine compound, a carbazole compound, an aromatic hydrocarbon, and ahigh molecular compound (such as an oligomer, a dendrimer, or a polymer)can be used. The organic compound used for the composite material ispreferably an organic compound having a high hole-transport property.Specifically, a substance having a hole mobility of 1×10⁻⁶ cm²/Vs orhigher is preferably used. Note that any other substance may be used aslong as the substance has a hole-transport property higher than anelectron-transport property. Specific examples of the organic compoundthat can be used as a substance having a hole-transport property in thecomposite material are given below.

Examples of the aromatic amine compound areN,N′-di(p-tolyl)-N,N-diphenyl-p-phenylenediamine (abbreviation: DTDPPA),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),N,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD),1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B), and the like.

Specific examples of the carbazole compound that can be used for thecomposite material are3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), and the like.

Other examples of the carbazole compound that can be used for thecomposite material are 4,4′-di(N-carbazolyl)biphenyl (abbreviation:CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB),9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA),1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, and thelike.

Examples of the aromatic hydrocarbon that can be used for the compositematerial are 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation:t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene,9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA),2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA),9,10-di(2-naphthyl)anthracene (abbreviation: DNA),9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene(abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene(abbreviation: DMNA),2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene,9,10-bis[2-(1-naphthyl)phenyl]anthracene,2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene,2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9′-bianthryl,10,10′-diphenyl-9,9′-bianthryl,10,10′-bis(2-phenylphenyl)-9,9′-bianthryl,10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl, anthracene,tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, andthe like. Other examples are pentacene, coronene, and the like. Thearomatic hydrocarbon having a hole mobility of 1×10⁻⁶ cm²/Vs or more andhaving 14 to 42 carbon atoms is particularly preferable.

The aromatic hydrocarbon that can be used for the composite material mayhave a vinyl skeleton. Examples of the aromatic hydrocarbon having avinyl group are 4,4′-bis(2,2-diphenylvinyl)biphenyl (abbreviation:DPVBi), 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation:DPVPA), and the like.

Other examples are high molecular compounds such aspoly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine)(abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), andpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:poly-TPD).

The hole-transport layer 112 is a layer containing a substance having ahole-transport property. As the substance having a hole-transportproperty, those given above as the substances having hole-transportproperties, which can be used for the above composite material, can beused. Note that detailed description is omitted to avoid repetition.Refer to the description of the composite material. Note that thecompound with a benzofuropyrimidine skeleton that is described inEmbodiment 1 may be contained in the hole-transport layer.

The light-emitting layer 113 is a layer containing a light-emittingsubstance. The light-emitting layer 113 may be formed using a filmcontaining only a light-emitting substance or a film in which alight-emitting substance is dispersed in a host material.

There is no particular limitation on a material that can be used as thelight-emitting substance in the light-emitting layer 113, and lightemitted from the material may be either fluorescence or phosphorescence.Examples of the above light-emitting substance are fluorescentsubstances and phosphorescent substances. Examples of the fluorescentsubstance areN,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6FLPAPrn),N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA),N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), coumarin 30,N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCABPhA),N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPABPhA),9,10-bis(1,1′-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine(abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine(abbreviation: DPhAPhA), coumarin 545T, N,N′-diphenylquinacridone(abbreviation: DPQd), rubrene,5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT),2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile(abbreviation: DCM1),2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCM2),N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation:p-mPhTD),7,14-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine(abbreviation: p-mPhAFD),2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTI),2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTB),2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile(abbreviation: BisDCM),2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: BisDCJTM),N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6FLPAPrn), and the like. Examples of blue-emissivephosphorescent substances include an organometallic iridium complexhaving a 4H-triazole skeleton, such astris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp)₃]),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]), ortris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPrptz-3b)₃]); an organometallic iridium complexhaving a 1H-triazole skeleton, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz1-mp)₃]) ortris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Prptz1-Me)₃]); an organometallic iridium complexhaving an imidazole skeleton, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III)(abbreviation: [Ir(iPrpmi)₃]), ortris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: Ir(dmpimpt-Me)₃); and an organometallic iridium complexin which a phenylpyridine derivative having an electron-withdrawinggroup is a ligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III) picolinate(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)]), orbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIr(acac)). Note that an organometalliciridium complex having a 4H-triazole skeleton has excellent reliabilityand emission efficiency and thus is especially preferable. Examples ofgreen-emissive phosphorescent substances include an organometalliciridium complex having a pyrimidine skeleton, such astris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(mppm)₃]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₃)),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₂(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(nbppm)₂(acac)]),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]), or(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]); an organometallic iridium complexhaving a pyrazine skeleton, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]) or(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]); an organometallic iridium complexhaving a pyridine skeleton, such astris(2-phenylpyridinato-N,C^(2′))iridium(III) (abbreviation:[Ir(ppy)₃]), bis(2-phenylpyridinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(ppy)₂(acac)]),bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation:[Ir(bzq)₂(acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation:[Ir(bzq)₃]), tris(2-phenylquinolinato-N,C^(2′))iridium(III)(abbreviation: [Ir(pq)₃]), orbis(2-phenylquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(pq)₂(acac)]); and a rare earth metal complex such astris(acetylacetonato)(monophenanthroline)terbium(III)(abbreviation:Tb(acac)₃(Phen)). Note that an organometallic iridium complex having apyrimidine skeleton has distinctively high reliability and emissionefficiency and thus is especially preferable. Examples of red-emissivephosphorescent substances include an organometallic iridium complexhaving a pyrimidine skeleton, such as(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: [Ir(5mdppm)₂(dibm)]),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(5mdppm)₂(dpm)]), orbis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(d1npm)₂(dpm)]); an organometallic iridium complexhaving a pyrazine skeleton, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]), or(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]); an organometallic iridium complexhaving a pyridine skeleton, such astris(1-phenylisoquinolinato-N,C^(2′))iridium(III) (abbreviation:[Ir(piq)₃]) orbis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: [Ir(piq)₂(acac)]); a platinum complex such as2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II)(abbreviation: PtOEP); and a rare earth metal complex suchastris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]) ortris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]). Note that an organometallic iridiumcomplex having a pyrimidine skeleton has distinctively high reliabilityand emission efficiency and thus is especially preferable. Further,because an organometallic iridium complex having a pyrazine skeleton canprovide red light emission with favorable chromaticity, the use of theorganometallic iridium complex in a white light-emitting elementimproves a color rendering property of the white light-emitting element.Note that a compound with a benzofuropyrimidine skeleton exhibits lightin blue to ultraviolet regions, and thus can be used as a light-emittingmaterial. It is also possible to use a compound with abenzofuropyrimidine skeleton.

The material that can be used as the light-emitting substance may beselected from various substances as well as from the substances givenabove.

As a host material in which the light-emitting substance is dispersed,the compound with a benzofuropyrimidine skeleton is preferably used.

Since the compound with a benzofuropyrimidine skeleton has a wide bandgap and a high triplet excitation level (T₁ level), the compound can besuitably used as a host material in which a light-emitting substanceemitting high-energy light is dispersed, such as a fluorescent substanceemitting blue or a phosphorescent substance emitting a color betweengreen and blue. Needless to say, the compound can also be used as a hostmaterial in which a fluorescent substance emitting fluorescence having awavelength longer than the blue light wavelength or a phosphorescentsubstance emitting phosphorescence having a wavelength longer than thegreen light wavelength is dispersed. The carrier-transport property(specifically, the electron-transport property) of the compound is high;accordingly, a light-emitting element with low driving voltage can beprovided.

In addition, it is effective to use the compound with thebenzofuropyrimidine skeleton as a material of a carrier-transport layer(preferably an electron-transport layer) adjacent to a light-emittinglayer. Since the compound has a wide band gap or a high tripletexcitation level (T₁ level), even when the light-emitting substance is amaterial emitting high-energy light, such as a material emitting bluefluorescence or a material emitting green to blue phosphorescence, theenergy of carriers that have recombined in a host material can beeffectively transferred to the light-emitting substance. Thus, alight-emitting element having high emission efficiency can befabricated. Note that in the case where the compound is used as a hostmaterial or a material of a carrier-transport layer, the light-emittingmaterial is preferably, but not limited to, a substance having anarrower band gap than the compound or a substance having a lowersinglet excitation level (S₁ level) or a lower triplet excitation level(T₁ level) than the compound.

When the above compound with a benzofuropyrimidine skeleton is not usedas the host material, the following materials can be alternatively used.

The following are examples of materials having an electron-transportproperty: a metal complex such asbis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), orbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); aheterocyclic compound having a polyazole skeleton such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), or2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II); a heterocyclic compound having a diazineskeleton such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine(abbreviation: 4,6mPnP2Pm), or4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II); and a heterocyclic compound having a pyridine skeletonsuch as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation:35DCzPPy) or 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation:TmPyPB). Among the above materials, a heterocyclic compound having adiazine skeleton and a heterocyclic compound having a pyridine skeletonhave high reliability and are thus preferable. Specifically, aheterocyclic compound having a diazine (pyrimidine or pyrazine) skeletonhas a high electron-transport property to contribute to a reduction indriving voltage. Note that the above compound with a benzofuropyrimidineskeleton has a relatively high electron-transport property, and isclassified as a material having an electron-transport property.

The following are examples of materials which have a hole-transportproperty and can be used as the host material: a compound having anaromatic amine skeleton such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: mBPAFLP),4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP), 4,4′-diphenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBBi1BP),4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine(abbreviation: PCBAF), orN-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine(abbreviation: PCBASF); a compound having a carbazole skeleton such as1,3-bis(N-carbazolyl)benzene (abbreviation: mCP),4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), or3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP); a compound havinga thiophene skeleton such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), or4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV); and a compound having a furan skeleton suchas 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation:DBF3P-II) or4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II). Among the above materials, a compoundhaving an aromatic amine skeleton and a compound having a carbazoleskeleton are preferable because these compounds are highly reliable andhave high hole-transport properties to contribute to a reduction indriving voltage.

Note that when the light-emitting substance is a phosphorescentsubstance, a substance having a higher triplet excitation level (T₁level) than the phosphorescent substance is preferably selected as thehost material, and when the light-emitting substance is a fluorescentsubstance, a substance having a wider band gap than the fluorescentsubstance is preferably selected as the host material. Thelight-emitting layer may contain a third substance in addition to thehost material and the phosphorescent substance.

Here, to achieve high emission efficiency of a light-emitting elementthat uses a phosphorescent substance, energy transfer between the hostmaterial and the phosphorescent substance will be considered. Carrierrecombination occurs in both the host material and the phosphorescentsubstance; thus, efficient energy transfer from the host material to thephosphorescent substance is necessary to increase emission efficiency.

As mechanisms of the energy transfer from the host material to thephosphorescent substance, two mechanisms have been proposed: one isDexter mechanism, and the other is Förster mechanism. Each mechanism isdescribed below. Here, a molecule providing excitation energy isreferred to as a host molecule, while a molecule receiving theexcitation energy is referred to as a guest molecule.

<<Förster Mechanism (Dipole-Dipole Interaction)>>

Förster mechanism (also referred to as Förster resonance energytransfer) does not require direct contact between molecules for energytransfer. Through a resonant phenomenon of dipolar oscillation between ahost molecule and a guest molecule, energy transfer occurs. By theresonant phenomenon of dipolar oscillation, the host molecule providesenergy to the guest molecule, and thus, the host molecule returns to aground state and the guest molecule reaches an excited state. The rateconstant k_(h*→g) of Förster mechanism is expressed by Formula (1).

[Formula  1]                                       $\begin{matrix}{k_{h^{*}arrow g} = {\frac{9000c^{4}K^{2}\phi\mspace{14mu}\ln\mspace{14mu} 10}{128\pi^{5}n^{4}N\;\tau\; R^{6}}{\int{\frac{{f_{h}^{\prime}(v)}{ɛ_{g}(v)}}{v^{4}}{dv}}}}} & (1)\end{matrix}$

In Formula (1), v denotes a frequency, f_(h)(v) denotes a normalizedemission spectrum of a host molecule (a fluorescence spectrum in energytransfer from a singlet excited state, and a phosphorescence spectrum inenergy transfer from a triplet excited state), ε_(g)(v) denotes a molarabsorption coefficient of a guest molecule, N denotes Avogadro's number,n denotes a refractive index of a medium, R denotes an intermoleculardistance between the host molecule and the guest molecule, τ denotes ameasured lifetime of an excited state (fluorescence lifetime orphosphorescence lifetime), c denotes the speed of light, ϕ denotes aluminescence quantum yield (a fluorescence quantum yield in energytransfer from a singlet excited state, and a phosphorescence quantumyield in energy transfer from a triplet excited state), and K² denotes acoefficient (0 to 4) of orientation of a transition dipole momentbetween the host molecule and the guest molecule. Note that K²=⅔ inrandom orientation.

<<Dexter Mechanism (Electron Exchange Interaction)>>

In Dexter mechanism (also referred to as Dexter electron transfer), ahost molecule and a guest molecule are close to a contact effectiverange where their orbitals can overlap, and the host molecule in anexcited state and the guest molecule in a ground state exchange theirelectrons, which leads to energy transfer. The rate constant k_(h*→g) ofDexter mechanism is expressed by Formula (2).

[Formula  2]                                       $\begin{matrix}{k_{h^{*}arrow g} = {( \frac{2\pi}{h} )K^{2}\mspace{14mu}{\exp( {- \frac{2R}{L}} )}{\int{{f_{h}^{\prime}(v)}{ɛ_{g}^{\prime}(v)}{dv}}}}} & (2)\end{matrix}$

In Formula (2), h denotes a Planck constant, K denotes a constant havingan energy dimension, v denotes a frequency, f_(h)(v) denotes anormalized emission spectrum of a host molecule (a fluorescence spectrumin energy transfer from a singlet excited state, and a phosphorescencespectrum in energy transfer from a triplet excited state), ε′_(g)(v)denotes a normalized absorption spectrum of a guest molecule, L denotesan effective molecular radius, and R denotes an intermolecular distancebetween the host molecule and the guest molecule.

Here, the efficiency of energy transfer from the host molecule to theguest molecule (energy transfer efficiency Φ_(ET)) is expressed byFormula (3). In the formula, k_(r) denotes a rate constant of alight-emission process (fluorescence in energy transfer from a singletexcited state, and phosphorescence in energy transfer from a tripletexcited state), k_(n) denotes a rate constant of a non-light-emissionprocess (thermal deactivation or intersystem crossing), and τ denotes ameasured lifetime of an excited state.

[Formula  3]                                       $\begin{matrix}{\Phi_{ET} = {\frac{k_{h^{*}arrow g}}{k_{r} + k_{n} + k_{h^{*}arrow g}} = \frac{k_{h^{*}arrow g}}{( \frac{1}{\tau} ) + k_{h^{*}arrow g}}}} & (3)\end{matrix}$

First, according to Formula (3), it is understood that the energytransfer efficiency Φ_(ET) can be increased by significantly increasingthe rate constant k_(h*→g) of energy transfer as compared with anothercompeting rate constant k_(r)+k_(n) (=1/τ). Then, in order to increasethe rate constant k_(h*→g) of energy transfer, based on Formulae (1) and(2), in Förster mechanism and Dexter mechanism, it is preferable that anemission spectrum of a host molecule (a fluorescence spectrum in energytransfer from a singlet excited state, and a phosphorescence spectrum inenergy transfer from a triplet excited state) has a large overlap withan absorption spectrum of a guest molecule.

Here, a longest-wavelength-side (lowest-energy-side) absorption band inthe absorption spectrum of the guest molecule is important inconsidering the overlap between the emission spectrum of the hostmolecule and the absorption spectrum of the guest molecule.

In this embodiment, a phosphorescent compound is used as the guestmaterial. In an absorption spectrum of the phosphorescent compound, anabsorption band that is considered to contribute to light emission mostgreatly is at an absorption wavelength corresponding to directtransition from a ground state to a triplet excited state and a vicinityof the absorption wavelength, which is on the longest wavelength side.Therefore, it is considered preferable that the emission spectrum (afluorescence spectrum and a phosphorescence spectrum) of the hostmaterial overlap with the absorption band on the longest wavelength sidein the absorption spectrum of the phosphorescent compound.

For example, most organometallic complexes, especially light-emittingiridium complexes, have a broad absorption band around 500 nm to 600 nmas the absorption band on the longest wavelength side. This absorptionband is mainly based on a triplet MLCT (metal to ligand charge transfer)transition. Note that it is considered that the absorption band alsoincludes absorptions based on a triplet π-π* transition and a singletMLCT transition, and that these absorptions overlap each other to form abroad absorption band on the longest wavelength side in the absorptionspectrum. Therefore, when an organometallic complex (especially iridiumcomplex) is used as the guest material, it is preferable to make thebroad absorption band on the longest wavelength side have a largeoverlap with the emission spectrum of the host material as describedabove.

Here, first, energy transfer from a host material in a triplet excitedstate will be considered. From the above-described discussion, it ispreferable that, in energy transfer from a triplet excited state, thephosphorescence spectrum of the host material and the absorption band onthe longest wavelength side of the guest material have a large overlap.

However, a question here is energy transfer from the host molecule inthe singlet excited state. In order to efficiently perform not onlyenergy transfer from the triplet excited state but also energy transferfrom the singlet excited state, it is clear from the above-describeddiscussion that the host material needs to be designed such that notonly its phosphorescence spectrum but also its fluorescence spectrumoverlaps with the absorption band on the longest wavelength side of theguest material. In other words, unless the host material is designed soas to have its fluorescence spectrum in a position similar to that ofits phosphorescence spectrum, it is not possible to achieve efficientenergy transfer from the host material in both the singlet excited stateand the triplet excited state.

However, in general, the S₁ level differs greatly from the T₁ level (S₁level>T₁ level); therefore, the fluorescence emission wavelength alsodiffers greatly from the phosphorescence emission wavelength(fluorescence emission wavelength<phosphorescence emission wavelength).For example, 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), which iscommonly used in a light-emitting element containing a phosphorescentcompound, has a phosphorescence spectrum around 500 nm and has afluorescence spectrum around 400 nm, which are largely different byabout 100 nm. This example also shows that it is extremely difficult todesign a host material so as to have its fluorescence spectrum in aposition similar to that of its phosphorescence spectrum.

Also, since the S₁ level is higher than the T₁ level, the T₁ level of ahost material whose fluorescence spectrum corresponds to a wavelengthclose to an absorption spectrum of a guest material on the longestwavelength side is lower than the T₁ level of the guest material.

Thus, in the case where a phosphorescent substance is used as thelight-emitting substance, it is preferable that the light-emitting layerinclude a third substance in addition to the host material and thelight-emitting substance and a combination of the host material and thethird substance form an exciplex (also referred to as an excitedcomplex).

In that case, at the time of recombination of carriers (electrons andholes) in the light-emitting layer, the host material and the thirdsubstance form an exciplex. A fluorescence spectrum of the exciplex ison a longer wavelength side than a fluorescence spectrum of the hostmaterial alone or the third substance alone. Therefore, energy transferfrom a singlet excited state can be maximized while the T₁ levels of thehost material and the third substance are kept higher than the T₁ levelof the guest material. In addition, the exciplex is in a state where theT₁ level and the S₁ level are close to each other; therefore, thefluorescence spectrum and the phosphorescence spectrum exist atsubstantially the same position. Accordingly, both the fluorescencespectrum and the phosphorescence spectrum of the exciplex can have alarge overlap with an absorption corresponding to transition of theguest molecule from the singlet ground state to the triplet excitedstate (a broad absorption band of the guest molecule existing on thelongest wavelength side in the absorption spectrum), and thus alight-emitting element having high energy transfer efficiency can beobtained.

As the third substance, the above material which can be used as the hostmaterial or additives can be used. There is no particular limitation onthe host materials and the third substance as long as they can form anexciplex; a combination of a compound which readily accepts electrons (acompound having an electron-transport property) and a compound whichreadily accepts holes (a compound having a hole-transport property) ispreferably employed.

In the case where a compound having an electron-transport property and acompound having a hole-transport property are used for the host materialand the third substance, carrier balance can be controlled by themixture ratio of the compounds. Specifically, the ratio of the hostmaterial to the third substance (or additive) is preferably from 1:9 to9:1. Note that in that case, the following structure may be employed: alight-emitting layer in which one kind of a light-emitting substance isdispersed is divided into two layers, and the two layers have differentmixture ratios of the host material to the third substance. With thisstructure, the carrier balance of the light-emitting element can beoptimized, so that the lifetime of the light-emitting element can beimproved. Furthermore, one of the light-emitting layers may be ahole-transport layer and the other of the light-emitting layers may bean electron-transport layer.

In the case where the light-emitting layer having the above-describedstructure is formed using a plurality of materials, the light-emittinglayer can be formed using co-evaporation by a vacuum evaporation method;or an inkjet method, a spin coating method, a dip coating method, or thelike with a solution of the materials.

The electron-transport layer 114 is a layer containing a substancehaving an electron-transport property. For example, theelectron-transport layer 114 is formed using a metal complex having aquinoline skeleton or a benzoquinoline skeleton, such astris(8-quinolinolato)aluminum (abbreviation: Alq),tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), orbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq), or the like. A metal complex having an oxazole-based orthiazole-based ligand, such as bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(abbreviation: Zn(BOX)₂) or bis[2-(2-hydroxyphenyl)benzothiazolato]zinc(abbreviation: Zn(BTZ)₂), or the like can also be used. Other than themetal complexes,2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), or the like can also be used. Thesubstances given here are mainly ones having an electron mobility of10⁻⁶ cm²/Vs or higher. Note that any substance other than the abovesubstances may be used for the electron-transport layer as long as thesubstance has an electron-transport property higher than ahole-transport property.

The compound with a benzofuropyrimidine skeleton may also be used as amaterial contained in the electron-transport layer 114. The compoundwith a benzofuropyrimidine skeleton has a wide band gap and a hightriplet excitation level (T₁ level) and thus can effectively preventtransfer of excitation energy in the light-emitting layer to theelectron-transport layer 114 to inhibit a reduction in emissionefficiency due to the excitation energy transfer, and allow alight-emitting element having high emission efficiency to be fabricated.Moreover, the compound with a benzofuropyrimidine skeleton has a highcarrier-transport property; thus, a light-emitting element having lowdriving voltage can be provided.

The electron-transport layer is not limited to a single layer, and maybe a stack including two or more layers containing any of the abovesubstances.

Between the electron-transport layer and the light-emitting layer, alayer that controls transport of electron carriers may be provided. Thisis a layer formed by addition of a small amount of a substance having ahigh electron-trapping property to the aforementioned materials having ahigh electron-transport property, and the layer is capable of adjustingcarrier balance by retarding transport of electron carriers. Such astructure is very effective in preventing a problem (such as a reductionin element lifetime) caused when electrons pass through thelight-emitting layer.

It is preferable that the host material in the light-emitting layer anda material of the electron-transport layer have the same skeleton, inwhich case transfer of carriers can be smooth and thus the drivingvoltage can be reduced. Moreover, it is effective that the host materialand the material of the electron-transport layer be the same material.

The electron-injection layer 115 may be provided in contact with thesecond electrode 102 between the electron-transport layer 114 and thesecond electrode 102. For the electron-injection layer 115, lithium,calcium, lithium fluoride (LiF), cesium fluoride (CsF), or calciumfluoride (CaF₂) can be used. A composite material of a substance havingan electron-transport property and a substance exhibiting anelectron-donating property (hereinafter, simply referred to aselectron-donating substance) with respect to the substance having anelectron-transport property can also be used. Examples of theelectron-donating substance include an alkali metal, an alkaline earthmetal, and compounds thereof. Note that such a composite material ispreferably used for the electron-injection layer 115, in which caseelectrons are injected efficiently from the second electrode 102. Withthis structure, a conductive material as well as a material having a lowwork function can be used for the cathode.

For the electrode functioning as a cathode, any of metals, alloys,electrically conductive compounds, and mixtures thereof which have a lowwork function (specifically, a work function of 3.8 eV or less) or thelike can be used. Specific examples of such a cathode material includeelements that belong to Groups 1 and 2 of the periodic table, i.e.,alkali metals such as lithium (Li) and cesium (Cs), and alkaline earthmetals such as magnesium (Mg), calcium (Ca), and strontium (Sr), alloysthereof (e.g., MgAg or AlLi), rare earth metals such as europium (Eu)and ytterbium (Yb), alloys thereof, and the like. However, when theelectron-injection layer is provided between the second electrode 102and the electron-transport layer, for the second electrode 102, any of avariety of conductive materials such as Al, Ag, ITO, or indium oxide-tinoxide containing silicon or silicon oxide can be used regardless of thework function. Films of these electrically conductive materials can beformed by a sputtering method, an inkjet method, a spin coating method,or the like.

Any of a variety of methods can be used to form the EL layer 103regardless whether it is a dry process or a wet process. For example, avacuum evaporation method, an inkjet method, a spin coating method, orthe like may be used. Different formation methods may be used for theelectrodes or the layers.

In addition, the electrode may be formed by a wet method using a sol-gelmethod, or by a wet method using paste of a metal material.Alternatively, the electrode may be formed by a dry method such as asputtering method or a vacuum evaporation method.

Note that the structure of the EL layer provided between the firstelectrode 101 and the second electrode 102 is not limited to the abovestructure. However, it is preferable that a light-emitting region whereholes and electrons recombine be positioned away from the firstelectrode 101 and the second electrode 102 so as to prevent quenchingdue to the proximity of the light-emitting region and a metal used foran electrode or a carrier-injection layer.

Further, in order that transfer of energy from an exciton generated inthe light-emitting layer can be inhibited, preferably, thehole-transport layer and the electron-transport layer which are indirect contact with the light-emitting layer, particularly acarrier-transport layer in contact with a side closer to thelight-emitting region in the light-emitting layer 113 is formed with asubstance having a wider energy gap than the light-emitting substance ofthe light-emitting layer or the light-emitting substance included in thelight-emitting layer.

In the light-emitting element having the above-described structure,current flows due to a potential difference between the first electrode101 and the second electrode 102, and holes and electrons recombine inthe light-emitting layer 113 which contains a substance having a highlight-emitting property, so that light is emitted. In other words, alight-emitting region is formed in the light-emitting layer 113.

Light is extracted out through one or both of the first electrode 101and the second electrode 102. Therefore, one or both of the firstelectrode 101 and the second electrode 102 are light-transmittingelectrodes. In the case where only the first electrode 101 is alight-transmitting electrode, light is extracted from the substrate sidethrough the first electrode 101. In contrast, when only the secondelectrode 102 is a light-transmitting electrode, light is extracted fromthe side opposite to the substrate side through the second electrode102. In the case where both the first electrode 101 and the secondelectrode 102 are light-transmitting electrodes, light is extracted fromboth the substrate side and the side opposite to the substrate sidethrough the first electrode 101 and the second electrode 102.

Since the light-emitting element of this embodiment is formed using thecompound with a benzofuropyrimidine skeleton, which has a wide energygap, efficient light emission can be obtained even if a light-emittingsubstance is any of a fluorescent substance emitting blue and aphosphorescent substance emitting a color between green and blue, whichhave a wide energy gap, and the light-emitting element can have highemission efficiency. Thus, a light-emitting element with lower powerconsumption can be provided. Further, the compound with abenzofuropyrimidine skeleton has a high carrier-transport property;thus, a light-emitting element having low driving voltage can beprovided.

Such a light-emitting element may be fabricated using a substrate madeof glass, plastic, or the like as a support. A plurality of suchlight-emitting elements are formed over one substrate, thereby forming apassive matrix light-emitting device. Alternatively, a transistor may beformed over a substrate made of glass, plastic, or the like, and thelight-emitting element may be fabricated over an electrode electricallyconnected to the transistor. In this manner, an active matrixlight-emitting device in which the driving of the light-emitting elementis controlled by the transistor can be fabricated. Note that a structureof the transistor is not particularly limited. Either a staggered TFT oran inverted staggered TFT may be employed. In addition, thecrystallinity of a semiconductor used for the TFT is not particularlylimited. In addition, a driver circuit formed in a TFT substrate may beformed with n-type TFTs and p-type TFTs, or with either n-type TFTs orp-type TFTs. The semiconductor layer for forming the TFTs may be formedusing any material as long as the material exhibits semiconductorcharacteristics; for example, an element belonging to Group 14 of theperiodic table such as silicon (Si) and germanium (Ge), a compound suchas gallium arsenide and indium phosphide, an oxide such as zinc oxideand tin oxide, and the like can be given. For the oxide exhibitingsemiconductor characteristics (oxide semiconductor), composite oxide ofan element selected from indium, gallium, aluminum, zinc, and tin can beused. Examples thereof are zinc oxide (ZnO), indium oxide containingzinc oxide (indium zinc oxide), and oxide containing indium oxide,gallium oxide, and zinc oxide (IGZO: indium gallium zinc oxide). Anorganic semiconductor may also be used. The semiconductor layer may haveeither a crystalline structure or an amorphous structure. Specificexamples of the crystalline semiconductor layer are a single crystalsemiconductor, a polycrystalline semiconductor, and a microcrystallinesemiconductor.

Embodiment 4

In this embodiment is described one mode of a light-emitting elementhaving a structure in which a plurality of light-emitting units arestacked (hereinafter, also referred to as stacked-type element), withreference to FIG. 1B. This light-emitting element includes a pluralityof light-emitting units between a first electrode and a secondelectrode. Each light-emitting unit can have the same structure as theEL layer 103 which is described in Embodiment 3. In other words, thelight-emitting element described in Embodiment 3 is a light-emittingelement having one light-emitting unit while the light-emitting elementdescribed in this embodiment is a light-emitting element having aplurality of light-emitting units.

In FIG. 1B, a first light-emitting unit 511 and a second light-emittingunit 512 are stacked between a first electrode 501 and a secondelectrode 502, and a charge generation layer 513 is provided between thefirst light-emitting unit 511 and the second light-emitting unit 512.The first electrode 501 and the second electrode 502 respectivelycorrespond to the first electrode 101 and the second electrode 102 inEmbodiment 3, and materials described in Embodiment 3 can be used.Further, the structures of the first light-emitting unit 511 and thesecond light-emitting unit 512 may be the same or different.

The charge generation layer 513 includes a composite material of anorganic compound and a metal oxide. As this composite material of anorganic compound and a metal oxide, the composite material that can beused for the hole-injection layer and described in Embodiment 3 can beused. As the organic compound, any of a variety of compounds such asaromatic amine compounds, carbazole compounds, aromatic hydrocarbons,and high molecular compounds (oligomers, dendrimers, polymers, or thelike) can be used. Note that the organic compound preferably has a holemobility of 1×10⁻⁶ cm²/Vs or more. However, any other substance may beused as long as the substance has a hole-transport property higher thanan electron-transport property. Since a composite material of an organiccompound and a metal oxide is excellent in carrier-injection propertyand carrier-transport property, low voltage driving and low currentdriving can be achieved. Note that in the light-emitting unit whoseanode side surface is in contact with the charge generation layer, ahole-transport layer is not necessarily provided because the chargegeneration layer can also function as the hole-transport layer.

The charge generation layer 513 may have a stacked-layer structure of alayer containing the composite material of an organic compound and ametal oxide and a layer containing another material. For example, alayer containing the composite material of an organic compound and ametal oxide may be combined with a layer containing a compound of asubstance selected from electron-donating substances and a compoundhaving a high electron-transport property. Moreover, the chargegeneration layer 513 may be formed by combining a layer containing thecomposite material of an organic compound and a metal oxide with atransparent conductive film.

The charge generation layer 513 provided between the firstlight-emitting unit 511 and the second light-emitting unit 512 may haveany structure as long as electrons can be injected to a light-emittingunit on one side and holes can be injected to a light-emitting unit onthe other side when a voltage is applied between the first electrode 501and the second electrode 502. For example, in FIG. 1B, any layer can beused as the charge generation layer 513 as long as the layer injectselectrons into the first light-emitting unit 511 and holes into thesecond light-emitting unit 512 when a voltage is applied such that thepotential of the first electrode is higher than that of the secondelectrode.

Although the light-emitting element having two light-emitting units isdescribed in this embodiment, the present invention can be similarlyapplied to a light-emitting element in which three or morelight-emitting units are stacked. With a plurality of light-emittingunits partitioned by the charge generation layer between a pair ofelectrodes, as in the light-emitting element according to thisembodiment, light with high luminance can be obtained while currentdensity is kept low; thus, a light-emitting element having a longlifetime can be obtained. In addition, a low power consumptionlight-emitting device which can be driven at low voltage can beachieved.

By making the light-emitting units emit light of different colors fromeach other, the light-emitting element can provide light emission of adesired color as a whole. For example, by forming a light-emittingelement having two light-emitting units such that the emission color ofthe first light-emitting unit and the emission color of the secondlight-emitting unit are complementary colors, the light-emitting elementcan provide white light emission as a whole. Note that the word“complementary” means color relationship in which an achromatic color isobtained when colors are mixed. In other words, when lights obtainedfrom substances which emit light of complementary colors are mixed,white light emission can be obtained. Further, the same can be appliedto a light-emitting element having three light-emitting units. Forexample, the light-emitting element as a whole can provide white lightemission when the emission color of the first light-emitting unit isred, the emission color of the second light-emitting unit is green, andthe emission color of the third light-emitting unit is blue.Alternatively, in the case of employing a light-emitting element inwhich a phosphorescent substance is used for a light-emitting layer ofone light-emitting unit and a fluorescent substance is used for alight-emitting layer of the other light-emitting unit, both fluorescenceand phosphorescence can be efficiently emitted from the light-emittingelement. For example, when red phosphorescence and green phosphorescenceare obtained from one light-emitting unit and blue fluorescence isobtained from the other light-emitting unit, white light with highemission efficiency can be obtained.

Since the light-emitting element of this embodiment contains thecompound with a benzofuropyrimidine skeleton, the light-emitting elementcan have high emission efficiency or operate at low driving voltage. Inaddition, since light emission with high color purity which is derivedfrom the light-emitting substance can be obtained from thelight-emitting unit including the compound, color adjustment of thelight-emitting element as a whole is easy.

Note that this embodiment can be combined with any of the otherembodiments as appropriate.

Embodiment 5

In this embodiment, a light-emitting device that uses a light-emittingelement including a compound with a benzofuropyrimidine skeleton will bedescribed.

In this embodiment, explanation will be given with reference to FIGS. 3Aand 3B of an example of the light-emitting device fabricated using alight-emitting element including a compound with a benzofuropyrimidineskeleton. Note that FIG. 3A is a top view of the light-emitting deviceand FIG. 3B is a cross-sectional view taken along the lines A-B and C-Din FIG. 3A. This light-emitting device includes a driver circuit portion(source side driver circuit) 601, a pixel portion 602, and a drivercircuit portion (gate side driver circuit) 603, which control lightemission of a light-emitting element 618 and denoted by dotted lines. Areference numeral 604 denotes a sealing substrate; 625, a desiccant;605, a sealing material; and 607, a space surrounded by the sealingmaterial 605.

Reference numeral 608 denotes a wiring for transmitting signals to beinput to the source side driver circuit 601 and the gate side drivercircuit 603 and receiving signals such as a video signal, a clocksignal, a start signal, and a reset signal from an FPC (flexible printedcircuit) 609 serving as an external input terminal. Although only theFPC is illustrated here, a printed wiring board (PWB) may be attached tothe FPC. The light-emitting device in the present specificationincludes, in its category, not only the light-emitting device itself butalso the light-emitting device provided with the FPC or the PWB.

Next, a cross-sectional structure is explained with reference to FIG.3B. The driver circuit portion and the pixel portion are formed over anelement substrate 610; here, the source line driver circuit 601, whichis a driver circuit portion, and one of the pixels in the pixel portion602 are shown.

As the source line driver circuit 601, a CMOS circuit in which ann-channel TFT 623 and a p-channel TFT 624 are combined is formed. Inaddition, the driver circuit may be formed with any of a variety ofcircuits such as a CMOS circuit, a PMOS circuit, and an NMOS circuit.Although a driver integrated type in which the driver circuit is formedover the substrate is illustrated in this embodiment, the driver circuitis not necessarily formed over the substrate, and the driver circuit canbe formed outside, not over the substrate.

The pixel portion 602 includes a plurality of pixels including aswitching TFT 611, a current controlling TFT 612, and a first electrode613 electrically connected to a drain of the current controlling TFT612. Note that to cover an end portion of the first electrode 613, aninsulator 614 is formed, for which a positive photosensitive resin filmis used here.

In order to improve coverage of a film formed over the insulator 614,the insulator 614 is formed to have a curved surface with curvature atits upper or lower end portion. For example, in the case where apositive photosensitive acrylic resin is used for a material of theinsulator 614, only the upper end portion of the insulator 614preferably has a surface with a curvature radius (0.2 μm to 3 μm). Asthe insulator 614, either a negative photosensitive material or apositive photosensitive material can be used.

An EL layer 616 and a second electrode 617 are formed over the firstelectrode 613. As a material used for the first electrode 613 whichfunctions as an anode, a material having a high work function ispreferably used. For example, a single-layer film of an ITO film, anindium tin oxide film containing silicon, an indium oxide filmcontaining zinc oxide at 2 wt % to 20 wt %, a titanium nitride film, achromium film, a tungsten film, a Zn film, a Pt film, or the like, astack including a titanium nitride film and a film containing aluminumas its main component, a stack including three layers of a titaniumnitride film, a film containing aluminum as its main component, and atitanium nitride film, or the like can be used. The stacked structureachieves low wiring resistance, a favorable ohmic contact, and afunction as an anode.

The EL layer 616 is formed by any of a variety of methods such as anevaporation method using an evaporation mask, an inkjet method, and aspin coating method. The EL layer 616 contains the compound with abenzofuropyrimidine skeleton. Further, for another material included inthe EL layer 616, any of low molecular-weight compounds and polymericcompounds (including oligomers and dendrimers) may be used.

As a material used for the second electrode 617, which is formed overthe EL layer 616 and functions as a cathode, a material having a lowwork function (e.g., Al, Mg, Li, Ca, or an alloy or compound thereof,such as MgAg, MgIn, or AlLi) is preferably used. In the case where lightgenerated in the EL layer 616 passes through the second electrode 617, astack including a thin metal film and a transparent conductive film(e.g., ITO, indium oxide containing zinc oxide at 2 wt % to 20 wt %,indium tin oxide containing silicon, or zinc oxide (ZnO)) is preferablyused for the second electrode 617.

Note that the light-emitting element is formed with the first electrode613, the EL layer 616, and the second electrode 617. The light-emittingelement has the structure described in Embodiment 3 or 4. In thelight-emitting device of this embodiment, the pixel portion, whichincludes a plurality of light-emitting elements, may include both thelight-emitting element with the structure described in Embodiment 3 or 4and a light-emitting element with a structure other than those.

The sealing substrate 604 is attached to the element substrate 610 withthe sealing material 605, so that the light-emitting element 618 isprovided in the space 607 surrounded by the element substrate 610, thesealing substrate 604, and the sealing material 605. The space 607 isfilled with filler. The filler may be an inert gas (such as nitrogen orargon), a resin, or a resin and/or a desiccant.

An epoxy-based resin or glass frit is preferably used for the sealingmaterial 605. It is preferable that such a material do not transmitmoisture or oxygen as much as possible. As the sealing substrate 604, aglass substrate, a quartz substrate, or a plastic substrate formed offiber reinforced plastic (FRP), poly(vinyl fluoride) (PVF), a polyester,an acrylic resin, or the like can be used.

As described above, the light-emitting device fabricated by using thelight-emitting element that contains the compound with abenzofuropyrimidine skeleton can be obtained.

FIGS. 4A and 4B illustrates examples of light-emitting devices in whichfull color display is achieved by forming a light-emitting elementexhibiting white light emission and providing a coloring layer (a colorfilter) and the like. In FIG. 4A, a substrate 1001, a base insulatingfilm 1002, a gate insulating film 1003, gate electrodes 1006, 1007, and1008, a first interlayer insulating film 1020, a second interlayerinsulating film 1021, a peripheral portion 1042, a pixel portion 1040, adriver circuit portion 1041, first electrodes 1024W, 1024R, 1024G, and1024B of light-emitting elements, a partition wall 1025, an EL layer1028, a second electrode 1029 of the light-emitting elements, a sealingsubstrate 1031, a sealant 1032, and the like are illustrated.

In FIG. 4A, coloring layers (a red coloring layer 1034R, a greencoloring layer 1034G, and a blue coloring layer 1034B) are provided on atransparent base material 1033. Further, a black layer (a black matrix)1035 may be additionally provided. The transparent base material 1033provided with the coloring layers and the black layer is positioned andfixed to the substrate 1001. Note that the coloring layers and the blacklayer are covered with an overcoat layer 1036. In FIG. 4A, light emittedfrom some of the light-emitting layers does not pass through thecoloring layers, while light emitted from the others of thelight-emitting layers passes through the coloring layers. Since lightwhich does not pass through the coloring layers is white and light whichpasses through any one of the coloring layers is red, blue, or green, animage can be displayed using pixels of the four colors.

FIG. 4B illustrates an example in which coloring layers (a red coloringlayer 1034R, a green coloring layer 1034G, and a blue coloring layer1034B) are formed between the gate insulating film 1003 and the firstinterlayer insulating film 1020. As shown in FIG. 4B, the coloringlayers may be provided between the substrate 1001 and the sealingsubstrate 1031.

The above-described light-emitting device has a structure in which lightis extracted from the substrate 1001 side where the TFTs are formed (abottom emission structure), but may have a structure in which light isextracted from the sealing substrate 1031 side (a top emissionstructure). FIG. 5 is a cross-sectional view of a light-emitting devicehaving a top emission structure. In this case, a substrate which doesnot transmit light can be used as the substrate 1001. The process up tothe step of forming a connection electrode which connects the TFT andthe anode of the light-emitting element is performed in a manner similarto that of the light-emitting device having a bottom emission structure.Then, a third interlayer insulating film 1037 is formed to cover anelectrode 1022. This insulating film may have a planarization function.The third interlayer insulating film 1037 can be formed using a materialsimilar to that of the second interlayer insulating film, and canalternatively be formed using any other known material.

The first electrodes 1024W, 1024R, 1024G, and 1024B of thelight-emitting elements each serve as an anode here, but may serve as acathode. Further, in the case of a light-emitting device having a topemission structure as illustrated in FIG. 5 , the first electrodes arepreferably reflective electrodes. The EL layer 1028 is formed to have astructure similar to the structure described in Embodiments 3 and 4,with which white light emission can be obtained.

In FIGS. 4A and 4B and FIG. 5 , the structure of the EL layer forproviding white light emission can be achieved by, for example, using aplurality of light-emitting layers or using a plurality oflight-emitting units. Note that the structure to provide white lightemission is not limited to the above.

In the case of a top emission structure as illustrated in FIG. 5 ,sealing can be performed with the sealing substrate 1031 on which thecoloring layers (the red coloring layer 1034R, the green coloring layer1034G, and the blue coloring layer 1034B) are provided. The sealingsubstrate 1031 may be provided with the black layer (the black matrix)1035 which is positioned between pixels. The coloring layers (the redcoloring layer 1034R, the green coloring layer 1034G, and the bluecoloring layer 1034B) and the black layer (the black matrix) may becovered with the overcoat layer as described in FIG. 4A. Note that alight-transmitting substrate is used as the sealing substrate 1031.

Although an example in which full color display is performed using fourcolors of red, green, blue, and white is shown here, there is noparticular limitation and full color display using three colors of red,green, and blue may be performed.

Since the light-emitting device of this embodiment uses thelight-emitting element described in Embodiment 3 or 4 (thelight-emitting element including the compound with a benzofuropyrimidineskeleton), the light-emitting device can have favorable characteristics.Specifically, the compound with a benzofuropyrimidine skeleton has awide energy gap and a high triplet excitation level (T₁ level) and caninhibit energy transfer from a light-emitting substance; thus, alight-emitting element having high emission efficiency can be provided,leading to a light-emitting device having reduced power consumption.Furthermore, the compound with a benzofuropyrimidine skeleton has a highcarrier-transport property, so that a light-emitting element with lowdriving voltage can be provided, leading to a light-emitting device withlow driving voltage.

An active matrix light-emitting device is described above, whereas apassive matrix light-emitting device is described below. FIGS. 6A and 6Billustrate a passive matrix light-emitting device fabricated byapplication of the present invention. FIG. 6A is a perspective view ofthe light-emitting device, and FIG. 6B is a cross-sectional view of FIG.6A taken along line X-Y In FIGS. 6A and 6B, over a substrate 951, an ELlayer 955 is provided between an electrode 952 and an electrode 956. Anedge portion of the electrode 952 is covered with an insulating layer953. A partition layer 954 is provided over the insulating layer 953.The sidewalls of the partition layer 954 slope so that the distancebetween one sidewall and the other sidewall gradually decreases towardthe surface of the substrate. In other words, a cross section takenalong the direction of the short side of the partition layer 954 istrapezoidal, and the base (a side which is in the same direction as aplane direction of the insulating layer 953 and in contact with theinsulating layer 953) is shorter than the upper side (a side which is inthe same direction as the plane direction of the insulating layer 953and not in contact with the insulating layer 953). By providing thepartition layer 954 in such a manner, a defect of the light-emittingelement due to static electricity or the like can be prevented. Thepassive matrix light-emitting device can also be driven with low powerconsumption, by including the light-emitting element described inEmbodiment 3 or 4 (the light-emitting element including the compoundwith a benzofuropyrimidine skeleton) capable of operating at low drivingvoltage.

Since many minute light-emitting elements arranged in a matrix in thelight-emitting device described above can each be controlled, thelight-emitting device can be suitably used as a display device fordisplaying images.

Embodiment 6

In this embodiment, electronic devices each including the light-emittingelement described in Embodiment 3 or 4 will be described. Thelight-emitting element described in Embodiment 3 or 4 includes thecompound with a benzofuropyrimidine skeleton and thus has reduced powerconsumption; as a result, the electronic devices described in thisembodiment can each include a display portion having reduced powerconsumption. In addition, the electronic devices can have low drivingvoltage since the light-emitting element described in Embodiment 3 or 4has low driving voltage.

Examples of the electronic device to which the above light-emittingelement is applied include television devices (also referred to as TV ortelevision receivers), monitors for computers and the like, cameras suchas digital cameras and digital video cameras, digital photo frames,cellular phones (also referred to as mobile phones or mobile phonedevices), portable game machines, portable information terminals, audioplayback devices, large game machines such as pachinko machines, and thelike. Specific examples of these electronic devices are given below.

FIG. 7A illustrates an example of a television device. In the televisiondevice, a display portion 7103 is incorporated in a housing 7101. Inaddition, here, the housing 7101 is supported by a stand 7105. Thedisplay portion 7103 enables display of images and includeslight-emitting elements which are the same as the light-emitting elementdescribed in Embodiment 3 or 4 and arranged in a matrix. Thelight-emitting elements each include the compound with abenzofuropyrimidine skeleton and thus can have high emission efficiencyand low driving voltage. Therefore, the television device including thedisplay portion 7103 which is formed using the light-emitting elementscan have reduced power consumption and low driving voltage.

The television device can be operated with an operation switch of thehousing 7101 or a separate remote controller 7110. With operation keys7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television device is provided with a receiver, a modem,and the like. With the use of the receiver, general televisionbroadcasting can be received. Moreover, when the television device isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 7B illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnection port 7205, a pointing device 7206, and the like. Note thatthis computer is fabricated by using light-emitting elements arranged ina matrix in the display portion 7203, which are the same as thatdescribed in Embodiment 3 or 4. The light-emitting elements each includethe compound with a benzofuropyrimidine skeleton and thus can have highemission efficiency and low driving voltage. Therefore, the computerincluding the display portion 7203 which is formed using thelight-emitting elements can have reduced power consumption and lowdriving voltage.

FIG. 7C illustrates a portable game machine having two housings, ahousing 7301 and a housing 7302, which are connected with a jointportion 7303 so that the portable game machine can be opened or folded.A display portion 7304 including light-emitting elements which are thesame as that described in Embodiment 3 or 4 and arranged in a matrix isincorporated in the housing 7301, and a display portion 7305 isincorporated in the housing 7302. In addition, the portable game machineillustrated in FIG. 7C includes a speaker portion 7306, a recordingmedium insertion portion 7307, an LED lamp 7308, an input unit (anoperation key 7309, a connection terminal 7310, a sensor 7311 (a sensorhaving a function of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, odor, or infrared rays), anda microphone 7312), and the like. Needless to say, the structure of theportable game machine is not limited to the above as far as the displayportion including light-emitting elements which are the same as thatdescribed in Embodiment 3 or 4 and arranged in a matrix is used as atleast either the display portion 7304 or the display portion 7305, orboth, and the structure can include other accessories as appropriate.The portable game machine illustrated in FIG. 7C has a function ofreading out a program or data stored in a storage medium to display iton the display portion, and a function of sharing information withanother portable game machine by wireless communication. The portablegame machine illustrated in FIG. 7C can have a variety of functionswithout limitation to the above. Since the light-emitting elements usedin the display portion 7304 have high emission efficiency by includingthe compound with a benzofuropyrimidine skeleton, the portable gamemachine including the above-described display portion 7304 can be aportable game machine having reduced power consumption. Since thelight-emitting elements used in the display portion 7304 each have lowdriving voltage by including the compound with a benzofuropyrimidineskeleton, the portable game machine can also be a portable game machinehaving low driving voltage.

FIG. 7D illustrates an example of a mobile phone. A mobile phone isprovided with a display portion 7402 incorporated in a housing 7401,operation buttons 7403, an external connection port 7404, a speaker7405, a microphone 7406, and the like. Note that the mobile phone hasthe display portion 7402 including light-emitting elements which are thesame as that described in Embodiment 3 or 4 and arranged in a matrix.The light-emitting elements each include the compound with abenzofuropyrimidine skeleton and thus can have high emission efficiencyand low driving voltage. Therefore, the mobile phone including thedisplay portion 7402 which is formed using the light-emitting elementscan have reduced power consumption and low driving voltage.

When the display portion 7402 of the mobile phone illustrated in FIG. 7Dis touched with a finger or the like, data can be input into the mobilephone. In this case, operations such as making a call and creatinge-mail can be performed by touching the display portion 7402 with afinger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting information such ascharacters. The third mode is a display-and-input mode in which twomodes of the display mode and the input mode are combined.

For example, in the case of making a call or creating e-mail, acharacter input mode mainly for inputting characters is selected for thedisplay portion 7402 so that characters displayed on a screen can beinput. In this case, it is preferable to display a keyboard or numberbuttons on almost the entire screen of the display portion 7402.

When a detection device including a sensor for detecting inclination,such as a gyroscope or an acceleration sensor, is provided inside thecellular phone, display on the screen of the display portion 7402 can beautomatically changed by determining the orientation of the cellularphone (whether the cellular phone is placed horizontally or verticallyfor a landscape mode or a portrait mode).

The screen modes are switched by touch on the display portion 7402 oroperation with the operation buttons 7403 of the housing 7401. Thescreen modes can be switched depending on the kind of images displayedon the display portion 7402. For example, when a signal of an imagedisplayed on the display portion is a signal of moving image data, thescreen mode is switched to the display mode. When the signal is a signalof text data, the screen mode is switched to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed for a certain period while a signal detected by anoptical sensor in the display portion 7402 is detected, the screen modemay be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by touchon the display portion 7402 with the palm or the finger, wherebypersonal authentication can be performed. Further, by providing abacklight or a sensing light source which emits a near-infrared light inthe display portion, an image of a finger vein, a palm vein, or the likecan be taken.

Note that the structure described in this embodiment can be combinedwith any of the structures described in Embodiments 1 to 5 asappropriate.

As described above, the application range of the light-emitting devicehaving the light-emitting element described in Embodiment 3 or 4 whichincludes the compound with a benzofuropyrimidine skeleton is wide sothat this light-emitting device can be applied to electronic devices ina variety of fields. By using the compound with a benzofuropyrimidineskeleton, an electronic device having reduced power consumption and lowdriving voltage can be obtained.

The light-emitting element including the compound with abenzofuropyrimidine skeleton can also be used for a light source device.One mode of application of the light-emitting element including thecompound with a benzofuropyrimidine skeleton to a light source device isdescribed with reference to FIG. 8 . Note that the light source deviceincludes a light-emitting element including the compound with abenzofuropyrimidine skeleton as a light irradiation unit and at leastincludes an input-output terminal portion which supplies current to thelight-emitting element. Further, the light-emitting element ispreferably shielded from the outside atmosphere by sealing.

FIG. 8 illustrates an example of a liquid crystal display device usingthe light-emitting elements including the compound with abenzofuropyrimidine skeleton for a backlight. The liquid crystal displaydevice illustrated in FIG. 8 includes a housing 901, a liquid crystallayer 902, a backlight 903, and a housing 904. The liquid crystal layer902 is connected to a driver IC 905. The light-emitting elementincluding the above compound is used in the backlight 903, to whichcurrent is supplied through a terminal 906.

The light-emitting element including the above compound is used for thebacklight of the liquid crystal display device; thus, the backlight canhave reduced power consumption. In addition, the use of thelight-emitting element including the above compound enables fabricationof a planar-emission lighting device and further a larger-areaplanar-emission lighting device; therefore, the backlight can be alarger-area backlight, and the liquid crystal display device can also bea larger-area device. Furthermore, the backlight using thelight-emitting element including the above compound can be thinner thana conventional one; accordingly, the display device can also be thinner.

FIG. 9 illustrates an example in which the light-emitting elementincluding the compound with a benzofuropyrimidine skeleton is used for atable lamp which is a lighting device. The table lamp illustrated inFIG. 9 includes a housing 2001 and a light source 2002, and thelight-emitting element including the above compound is used for thelight source 2002.

FIG. 10 illustrates an example in which the light-emitting elementincluding the compound with a benzofuropyrimidine skeleton is used foran indoor lighting device 3001. Since the light-emitting elementincluding the above compound has reduced power consumption, a lightingdevice that has reduced power consumption can be obtained. Further,since the light-emitting element including the above compound can have alarge area, the light-emitting element can be used for a large-arealighting device. Furthermore, since the light-emitting element includingthe above compound is thin, a lighting device having a reduced thicknesscan be fabricated.

The light-emitting element including the compound with abenzofuropyrimidine skeleton can also be used for an automobilewindshield or an automobile dashboard. FIG. 11 illustrates one mode inwhich the light-emitting elements including the above compound are usedfor an automobile windshield and an automobile dashboard. Displayregions 5000 to 5005 each include the light-emitting element includingthe above compound.

The display regions 5000 and 5001 are display devices which are providedin the automobile windshield and in which light-emitting elementsincluding the above compound are incorporated. The light-emittingelement including the above compound can be formed into a so-calledsee-through display device, through which the opposite side can be seen,by including a first electrode and a second electrode formed ofelectrodes having light-transmitting properties. Such see-throughdisplay devices can be provided even in the windshield of the car,without hindering the vision. Note that in the case where a transistorfor driving the light-emitting element is provided, a transistor havinga light-transmitting property, such as an organic transistor using anorganic semiconductor material or a transistor using an oxidesemiconductor, is preferably used.

The display region 5002 is a display device which is provided in apillar portion and in which the light-emitting element including theabove compound is incorporated. The display region 5002 can compensatefor the view hindered by the pillar portion by showing an image taken byan imaging unit provided in the car body. Similarly, the display region5003 provided in the dashboard can compensate for the view hindered bythe car body by showing an image taken by an imaging unit provided inthe outside of the car body, which leads to elimination of blind areasand enhancement of safety. Showing an image so as to compensate for thearea which a driver cannot see makes it possible for the driver toconfirm safety easily and comfortably.

The display region 5004 and the display region 5005 can provide avariety of kinds of information such as navigation data, a speedometer,a tachometer, a mileage, a fuel meter, a gearshift indicator, andair-condition setting. The content or layout of the display can bechanged freely by a user as appropriate. Note that such information canalso be shown by the display regions 5000 to 5003. The display regions5000 to 5005 can also be used as lighting devices.

By including the compound with a benzofuropyrimidine skeleton, thelight-emitting element including the above compound has low drivingvoltage and lower power consumption. Therefore, load on a battery issmall even when a number of large screens such as the display regions5000 to 5005 are provided, which provides comfortable use. For thatreason, the light-emitting device and the lighting device each of whichincludes the light-emitting element including the above compound can besuitably used as an in-vehicle light-emitting device and lightingdevice.

FIGS. 12A and 12B illustrate an example of a foldable tablet terminal.FIG. 12A illustrates the tablet terminal which is unfolded. The tabletterminal includes a housing 9630, a display portion 9631 a, a displayportion 9631 b, a display mode switch 9034, a power switch 9035, apower-saving mode switch 9036, a clasp 9033, and an operation switch9038. Note that in the tablet terminal, one or both of the displayportion 9631 a and the display portion 9631 b is/are formed using alight-emitting device which includes a light-emitting element includingthe above compound.

Part of the display portion 9631 a can be a touchscreen region 9632 aand data can be input when a displayed operation key 9637 is touched.Although half of the display portion 9631 a has only a display functionand the other half has a touchscreen function, one embodiment of thepresent invention is not limited to the structure. The whole displayportion 9631 a may have a touchscreen function. For example, a keyboardis displayed on the entire region of the display portion 9631 a so thatthe display portion 9631 a is used as a touchscreen; thus, the displayportion 9631 b can be used as a display screen.

Like the display portion 9631 a, part of the display portion 9631 b canbe a touchscreen region 9632 b. When a keyboard display switching button9639 displayed on the touchscreen is touched with a finger, a stylus, orthe like, the keyboard can be displayed on the display portion 9631 b.

Touch input can be performed in the touchscreen region 9632 a and thetouchscreen region 9632 b at the same time.

The display mode switch 9034 can switch the display between portraitmode, landscape mode, and the like, and between monochrome display andcolor display, for example. The power-saving switch 9036 can controldisplay luminance in accordance with the amount of external light in useof the tablet terminal detected by an optical sensor incorporated in thetablet terminal. Another detection device including a sensor fordetecting inclination, such as a gyroscope or an acceleration sensor,may be incorporated in the tablet terminal, in addition to the opticalsensor.

Although FIG. 12A illustrates an example in which the display portion9631 a and the display portion 9631 b have the same display area, oneembodiment of the present invention is not limited to the example. Thedisplay portion 9631 a and the display portion 9631 b may have differentdisplay areas and different display quality. For example, one displaypanel may be capable of higher-definition display than the other displaypanel.

FIG. 12B illustrates the tablet terminal which is folded. The tabletterminal includes the housing 9630, a solar cell 9633, a charge anddischarge control circuit 9634, a battery 9635, and a DC-to-DC converter9636. As an example, FIG. 12B illustrates the charge and dischargecontrol circuit 9634 including the battery 9635 and the DC-to-DCconverter 9636.

Since the tablet terminal is foldable, the housing 9630 can be closedwhen the tablet terminal is not in use. As a result, the display portion9631 a and the display portion 9631 b can be protected, therebyproviding a tablet terminal with high endurance and high reliability forlong-term use.

The tablet terminal illustrated in FIGS. 12A and 12B can have otherfunctions such as a function of displaying various kinds of data (e.g.,a still image, a moving image, and a text image), a function ofdisplaying a calendar, a date, the time, or the like on the displayportion, a touch-input function operating or editing the data displayedon the display portion by touch input, and a function controllingprocessing by various kinds of software (programs).

The solar cell 9633 provided on a surface of the tablet terminal cansupply power to the touchscreen, the display portion, a video signalprocessing portion, or the like. Note that the solar cell 9633 ispreferably provided on one or two surfaces of the housing 9630, in whichcase the battery 9635 can be charged efficiently.

The structure and operation of the charge and discharge control circuit9634 illustrated in FIG. 12B will be described with reference to a blockdiagram of FIG. 12C. FIG. 12C illustrates the solar cell 9633, thebattery 9635, the DC-to-DC converter 9636, a converter 9638, switchesSW1 to SW3, and the display portion 9631. The battery 9635, the DC-to-DCconverter 9636, the converter 9638, and the switches SW1 to SW3correspond to the charge and discharge control circuit 9634 illustratedin FIG. 12B.

First, description is made on an example of the operation in the casewhere power is generated by the solar cell 9633 with the use of externallight. The voltage of the power generated by the solar cell is raised orlowered by the DC-to-DC converter 9636 so as to be voltage for chargingthe battery 9635. Then, when power supplied from the battery 9635charged by the solar cell 9633 is used for the operation of the displayportion 9631, the switch SW1 is turned on and the voltage of the poweris raised or lowered by the converter 9638 so as to be voltage neededfor the display portion 9631. When images are not displayed on thedisplay portion 9631, the switch SW1 is turned off and the switch SW2 isturned on so that the battery 9635 is charged.

Although the solar cell 9633 is described as an example of a powergeneration unit, the power generation unit is not particularly limited,and the battery 9635 may be charged by another power generation unitsuch as a piezoelectric element or a thermoelectric conversion element(Peltier element). The battery 9635 may be charged by a non-contactpower transmission module which is capable of charging by transmittingand receiving power by wireless (without contact), or another chargeunit used in combination, and the power generation unit is notnecessarily provided.

Needless to say, one embodiment of the present invention is not limitedto the electronic device having the shape illustrated in FIGS. 12A to12C as long as the display portion 9631 is included.

Example 1 Synthesis Example 1

In this synthesis example, a method for synthesizing4-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]benzofuro[3,2-d]pyrimidine(abbreviation: 4mDBTBPBfpm-II) that is a compound having abenzofuropyrimidine skeleton and represented by Structural Formula (100)in Embodiment 1 will be described. The structural formula of4mDBTBPBfpm-II is shown below.

Step 1: Synthesis of 4-(3′-Bromobiphenyl-3-yl)dibenzothiophene

First, 48 g of 3-(dibenzothiophen-4-yl)phenylboronic acid, 54 g of3-iodobromobenzene, 1.9 g of tris(2-methylphenyl)phosphine(abbreviation: P(o-tolyl)₃), 160 mL of a 2M aqueous solution ofpotassium carbonate, 800 mL of toluene, and 80 mL of ethanol were put ina 3-L three-neck flask equipped with a reflux pipe. The air in the flaskwas replaced with nitrogen, and heating to 80° C. was performed fordissolution. To this mixed solution, 0.38 g of palladium(II) acetate wasadded and stirring was performed for 8 hours. Then, 0.92 g oftris(2-methylphenyl)phosphine and 0.18 g of palladium(II) acetate werefurther added and stirring was performed for 6 hours. After that, waterwas added to this solution and extraction with toluene was performed toobtain an organic layer. The organic layer was dried over magnesiumsulfate, and the dried solution was filtered. The solvent in thissolution was distilled off, and the resulting residue was dissolved inhot toluene. The hot toluene solution was subjected to hot filtrationthrough a filter aid in which Celite (Catalog No. 531-16855,manufactured by Wako Pure Chemical Industries, Ltd. (the same applies toCelite in the following description)), alumina, Florisil (Catalog No.540-00135, manufactured by Wako Pure Chemical Industries, Ltd. (the sameapplies to Florisil in the following description)), and Celite werestacked in this order. The solvent was distilled off and the resultingsolid was recrystallized from a mixed solvent of toluene and methanol,so that a white solid was obtained in a yield of 34%. Synthesis Scheme(a-1) of Step 1 is shown below.

Step 2: Synthesis of 3′-(Dibenzothiophen-4-yl)-3-biphenylboronic Acid

In a 1-L three-neck flask equipped with a dropping funnel was put 30 gof 4-(3′-bromobiphenyl-3-yl)dibenzothiophene obtained in Step 1, and theair in the flask was replaced with nitrogen. To the flask, 300 mL oftetrahydrofuran (dehydrated) was added, and the flask was cooled down to−78° C. in a cryostat. After that, 50 mL of a 1.6 M hexane solution ofn-butyl lithium was dropped with a dropping funnel, and 64 mL oftetrahydrofuran (dehydrated) was put in the dropping funnel to be pouredinto the reacted solution, which was then stirred at −78° C. for 1 hour.Then, 11 mL of trimethyl borate was dropped and the temperature wasraised to room temperature, at which stirring was performed for 18hours. To this solution, 48 mL of 1 M hydrochloric acid was added andstirring was performed for 1 hour. Water was added into the resultingmixture, and extraction with ethyl acetate was performed to give anorganic layer. The organic layer was washed with water and a saturatedaqueous solution of sodium chloride, and dried over magnesium sulfate.The solution obtained by the drying was filtered. The solvent in thissolution was distilled off, and the resulting solid was washed withtoluene; thus, a white solid was obtained in a yield of 40%. SynthesisScheme (b-1) of Step 2 is shown below.

Step 3: Synthesis of4-[3′-(Dibenzothiophen-4-yl)biphenyl-3-yl]benzofuro[3,2-d]pyrimidine(abbreviation: 4mDBTBPBfpm-II)

Into a 100-mL three-neck flask equipped with a reflux pipe were put 2.3g of 3′-(dibenzothiophen-4-yl)-3-biphenylboronic acid obtained in Step2, 1.2 g of 4-chlorobenzofuro[3,2-d]pyrimidine, 5.4 mL of a 2 M aqueoussolution of potassium carbonate, 27 mL of toluene, and 2.7 mL ofethanol. Degasification by stirring under a reduced pressure wasperformed and the air in the flask was replaced with nitrogen. To thismixture, 68 mg of tetrakis(triphenylphosphine)palladium(0)(abbreviation: Pd(PPh₃)₄) was added and the mixture was heated at 80° C.for 2 hours to cause a reaction. The resulting mixture was washed withwater and ethanol and recrystallized from toluene, so that 1.8 g of awhite solid was obtained in a yield of 60%. Synthesis Scheme (c-1) ofStep 3 is shown below.

By a train sublimation method, 2.3 g of the white solid was purified bysublimation. The sublimation purification was conducted under theconditions where the pressure was 3.2 Pa, the flow rate of an argon gaswas 15 mL/min, and the solid was heated at 235° C. After the sublimationpurification, 0.5 g of a white solid which was a target substance wasobtained at a collection rate of 22%.

By a train sublimation method, 1.5 g of a solid that was not purified bythe previous sublimation purification was subject to sublimationpurification. The sublimation purification was conducted under theconditions where the pressure was 2.7 Pa, the flow rate of an argon gaswas 5.0 mL/min, and the heating temperature was 245° C. After thesublimation purification, 1.4 g of a white solid which was a targetsubstance was obtained at a collection rate of 92%.

Analysis results by nuclear magnetic resonance (¹H-NMR) spectroscopy ofthe white solid obtained in Step 3 are described below. The resultsrevealed that 4mDBTBPBfpm-II was obtained.

¹H-NMR. δ(CDCl₃): 7.44-7.54 (m, 4H), 7.60-7.61 (m, 2H), 7.66-7.51 (m,4H), 7.78-7.84 (m, 2H), 7.91-7.92 (d, 1H), 8.17 (ts, 1H), 8.20-8.23 (m,2H), 8.31-8.32 (d, 1H), 8.62-8.63 (d, 1H), 8.96-8.97 (t, 1H), 9.30 (s,1H).

FIGS. 13A and 13B are ¹H NMR charts. Note that FIG. 13B shows anenlarged part of FIG. 13A in the range of 7.2 ppm to 8.8 ppm. Themeasurement results reveal that 4mDBTBPBfpm-II, which was the targetsubstance, was obtained.

<<Physical Properties of 4mDBTBPBfpm-II>>

FIG. 14A shows an absorption spectrum and an emission spectrum of4mDBTBPBfpm-II in a toluene solution of 4mDBTBPBfpm-II, and FIG. 14Bshows an absorption spectrum and an emission spectrum of a thin film of4mDBTBPBfpm-II. The spectra were measured with a UV-visiblespectrophotometer (V550, produced by JASCO Corporation). The spectra of4mDBTBPBfpm-II in the toluene solution of 4mDBTBPBfpm-II were measuredwith a toluene solution of 4mDBTBPBfpm-II put in a quartz cell. Thespectra of the thin film were measured with a sample prepared bydeposition of 4mDBTBPBfpm-II on a quartz substrate by evaporation. Notethat in the case of the absorption spectrum of 4mDBTBPBfpm-II in thetoluene solution of 4mDBTBPBfpm-II, the absorption spectrum obtained bysubtraction of the absorption spectra of quartz and toluene from themeasured spectra is shown in the drawing and that in the case of theabsorption spectrum of the thin film of 4mDBTBPBfpm-II, the absorptionspectrum obtained by subtraction of the absorption spectrum of thequartz substrate from the measured spectra is shown in the drawing.

As shown in FIG. 14A, in the case of 4mDBTBPBfpm-II in the toluenesolution, absorption peaks were observed at approximately 282 nm and 320nm. As shown in FIG. 14B, in the case of the thin film of4mDBTBPBfpm-II, absorption peaks were observed at approximately 244 nm,268 nm, 290 nm, 326 nm, and 340 nm, and an emission wavelength peak wasobserved at 410 nm (excitation wavelength: 340 nm). Thus, it was foundthat absorption and light emission of 4mDBTBPBfpm-II occur in extremelyshort wavelength regions.

The ionization potential of 4mDBTBPBfpm-II in a thin film state wasmeasured by a photoelectron spectrometer (AC-2, manufactured by RikenKeiki, Co., Ltd.) in the air. The obtained value of the ionizationpotential was converted into a negative value, so that the HOMO level of4mDBTBPBfpm-II was −6.38 eV From the data of the absorption spectrum ofthe thin film in FIG. 14B, the absorption edge of 4mDBTBPBfpm-II, whichwas obtained from Tauc plot with an assumption of direct transition, was3.50 eV. Therefore, the optical energy gap of 4mDBTBPBfpm-II in a solidstate was estimated at 3.50 eV; from the values of the HOMO levelobtained above and this energy gap, the LUMO level of 4mDBTBPBfpm-II wasestimated at −2.88 eV. This reveals that 4mDBTBPBfpm-II in the solidstate has an energy gap as wide as 3.50 eV.

Furthermore, 4mDBTBPBfpm-II was analyzed by liquid chromatography massspectrometry (LC/MS).

The analysis by LC/MS was carried out with Acquity UPLC (produced byWaters Corporation) and Xevo G2 Tof MS (produced by Waters Corporation).

In the MS analysis, ionization was carried out by an electrosprayionization (ESI) method. Capillary voltage and sample cone voltage wereset to 3.0 kV and 30 V, respectively. Detection was performed in apositive mode. A component which underwent the ionization under theabove-mentioned conditions was collided with an argon gas in a collisioncell to dissociate into product ions. Energy (collision energy) for thecollision with argon was 50 eV and 70 eV. A mass range for themeasurement was m/z=100 to 1200.

FIGS. 15A and 15B show the results. FIG. 15A shows the results at thetime when the collision energy was 50 eV. FIG. 15B shows the results atthe time when the collision energy was 70 eV.

Example 2 Synthesis Example 2

In this synthesis example, a synthesis example of4-{3-[3′-(9H-carbazol-9-yl)]biphenyl-3-yl}benzofuro[3,2-d]pyrimidine(abbreviation: 4mCzBPBfpm) that is a compound having abenzofuropyrimidine skeleton and represented by Structural Formula (300)in Embodiment 1 will be specifically described. The structural formulaof 4mCzBPBfpm is shown below.

Step 1: Synthesis of 9-[3-(3-Bromophenyl)phenyl]-9H-carbazole

First, 16 g (56 mmol) of 3-(9H-carbazol-9-yl)phenylboronic acid, 19 g(67 mmol) of 3-iodobromobenzene, 0.68 g (2.2 mmol) oftri(ortho-tolyl)phosphine, 56 mL of a 2 M aqueous solution of potassiumcarbonate, 250 mL of toluene, and 30 mL of ethanol were put into a 1-Lthree-neck flask, and the air in the flask was replaced with nitrogen.To this mixture was added 0.13 g (0.56 mmol) of palladium acetate, andthe mixture was heated and stirred at 80° C. for 14 hours. The aqueouslayer of the obtained reaction mixture was subjected to extraction withtoluene, and the resulting solution of the extract and the organic layerwere combined and washed with water and a saturated aqueous solution ofsodium chloride. Magnesium sulfate was added to the organic layer fordrying, and the resulting mixture was subjected to gravity filtration togive a filtrate. This filtrate was concentrated to give an oilysubstance. The oily substance was purified by recycling preparative HPLCusing LC-SakuraNEXT. The resulting fraction was concentrated and washedwith toluene and methanol; thus,9-[3-(3-bromophenyl)phenyl]-9H-carbazole was obtained as 13 g of a whitesolid in a yield of 58%. Synthesis Scheme (a-2) of Step 1 is shownbelow.

Step 2: Synthesis of 3-[3′-(9H-Carbazol-9-yl)]biphenylboronic Acid

In a 500-mL three-neck flask was put 13 g (33 mmol) of9-[3-(3-bromophenyl)phenyl]-9H-carbazole, the flask was degassed, andthe air in the flask was replaced with nitrogen. Then, 160 mL oftetrahydrofuran was added and stirring was performed at −78° C. To thismixed solvent, 24 mL (40 mmol) of n-butyl lithium (1.65 mol/L hexanesolution) was dropped and stirring was performed at −78° C. for 1 hour.After the predetermined time elapsed, 4.7 mL (43 mmol) of trimethylborate was added to this mixed solution, and stirring was performed for18 hours while the temperature was raised to 20° C. After thepredetermined time elapsed, 100 mL of 1 mol/L hydrochloric acid wasadded to the reacted solution, and stirring was performed at roomtemperature for 30 minutes. The aqueous layer of this mixture wassubjected to extraction with ethyl acetate, and the resulting solutionof the extract was washed with a saturated aqueous solution of sodiumchloride. Anhydrous magnesium sulfate was added to the organic layer fordrying, and the resulting mixture was subjected to gravity filtration.The filtrate was concentrated to give a solid. This solid was washedwith toluene, so that 3-[3′-(9H-carbazol-9-yl)]biphenylboronic acid wasobtained as 6.0 g of a white solid in a yield of 51%. Synthesis Scheme(b-2) of Step 2 is shown below.

Step 3: Synthesis of4-{3-[3′-(9H-Carbazol-9-yl)]biphenyl-3-yl}benzofuro[3,2-d]pyrimidine(abbreviation: 4mCzBPBfpm)

In a 200-mL three-neck flask were put 3.0 g (8.3 mmol) of3-[3′-(9H-carbazol-9-yl)]biphenylboronic acid, 1.7 g (8.3 mmol) of4-chlorobenzofuro[3,2-d]pyrimidine, 8.3 mL of a 2 M aqueous solution ofpotassium carbonate, 40 mL of toluene, and 4 mL of ethanol, and the airin the flask was replaced with nitrogen. To this mixture was added 68.3mg (0.059 mmol) of bis(triphenylphosphine)palladium(II) dichloride(Pd(PPh₃)₂Cl₂), and the mixture was heated and stirred at 80° C. for 6hours. The aqueous layer of the obtained reaction solution was subjectedto extraction with toluene, and the resulting solution of the extractand the organic layer were combined and washed with a saturated aqueoussolution of sodium chloride. Anhydrous magnesium sulfate was added tothe organic layer for drying, and the resulting mixture was subjected togravity filtration to give a filtrate. The filtrate was concentrated togive a solid. The solid was dissolved in toluene and this solution wasfiltered through Celite, alumina, and Celite. The filtrate wasconcentrated to give a solid. The solid was recrystallized from toluene,so that 2.0 g of a white solid was obtained in a yield of 50%. Then, 2.0g of the white solid was purified by sublimation using a trainsublimation method. The sublimation purification was conducted under theconditions where the pressure was 2.3 Pa, the flow rate of an argon gaswas 10 mL/min, and the solid was heated at 250° C. After the sublimationpurification, 1.3 g of a white solid which was a target substance wasobtained at a collection rate of 65%. Synthesis Scheme (c-2) of Step 2is shown below.

Analysis results by nuclear magnetic resonance (¹H-NMR) spectroscopy ofthe white solid obtained in Step 3 are described below.

¹H-NMR. δ(CDCl₃): 7.32 (m, 2H), 7.44 (m, 2H), 7.52-7.55 (m, 3H),7.63-7.64 (m, 1H), 7.69-7.77 (m, 4H), 7.85-7.88 (m, 2H), 7.97 (t, 1H),8.18 (d, 2H), 8.31 (d, 1H), 8.65 (m, 1H), 8.92 (t, 1H), 9.27 (s, 1H).

FIGS. 16A and 16B are ¹H NMR charts. Note that FIG. 16B shows anenlarged part of FIG. 16A in the range of 7.6 ppm to 9.4 ppm. Themeasurement results reveal that 4mCzBPBfpm, which was the targetsubstance, was obtained.

<<Physical Properties of 4mCzBPBfpm>>

FIG. 17A shows an absorption spectrum and an emission spectrum of4mCzBPBfpm in a toluene solution of 4mCzBPBfpm, and FIG. 17B shows anabsorption spectrum and an emission spectrum of a thin film of4mCzBPBfpm. The spectra were measured with a UV-visiblespectrophotometer (V550, produced by JASCO Corporation). The spectra of4mCzBPBfpm in the toluene solution of 4mCzBPBfpm were measured with atoluene solution of 4mCzBPBfpm put in a quartz cell. The spectra of thethin film were measured with a sample prepared by deposition of4mCzBPBfpm on a quartz substrate by evaporation. Note that in the caseof the absorption spectrum of 4mCzBPBfpm in the toluene solution of4mCzBPBfpm, the absorption spectrum obtained by subtraction of theabsorption spectra of quartz and toluene from the measured spectra isshown in the drawing and that in the case of the absorption spectrum ofthe thin film of 4mCzBPBfpm, the absorption spectrum obtained bysubtraction of the absorption spectrum of the quartz substrate from themeasured spectra is shown in the drawing.

As shown in FIG. 17A, in the case of 4mCzBPBfpm in the toluene solution,absorption peaks were observed at approximately 294 nm, 324 nm and 334nm, and the peak of the emission wavelength was at 422 nm (at anexcitation wavelength of 330 nm). As shown in FIG. 17B, in the case ofthe thin film of 4mCzBPBfpm, absorption peaks were observed atapproximately 207 nm, 243 nm, 262 nm, 289 nm, 295 nm, 326 nm, and 341 nmand an emission wavelength peak was observed at 440 nm (excitationwavelength: 341 nm). Thus, it was found that absorption and lightemission of 4mCzBPBfpm occur in extremely short wavelength regions.

The ionization potential of 4mCzBPBfpm in a thin film state was measuredby a photoelectron spectrometer (AC-2, manufactured by Riken Keiki, Co.,Ltd.) in the air. The obtained value of the ionization potential wasconverted into a negative value, so that the HOMO level of 4mCzBPBfpmwas −6.13 eV. From the data of the absorption spectrum of the thin filmin FIG. 17B, the absorption edge of 4mCzBPBfpm, which was obtained fromTauc plot with an assumption of direct transition, was 3.49 eVTherefore, the optical energy gap of 4mCzBPBfpm in a solid state wasestimated at 3.49 eV; from the values of the HOMO level obtained aboveand this energy gap, the LUMO level of 4mCzBPBfpm was estimated at −2.64eV This reveals that 4mCzBPBfpm in the solid state has an energy gap aswide as 3.49 eV.

Furthermore, 4mCzBPBfpm was analyzed by liquid chromatography massspectrometry (LC/MS).

The analysis by LC/MS was carried out with Acquity UPLC (produced byWaters Corporation) and Xevo G2 Tof MS (produced by Waters Corporation).

In the MS analysis, ionization was carried out by an electrosprayionization (ESI) method. Capillary voltage and sample cone voltage wereset to 3.0 kV and 30 V, respectively. Detection was performed in apositive mode. A component which underwent the ionization under theabove-mentioned conditions was collided with an argon gas in a collisioncell to dissociate into product ions. Energy (collision energy) for thecollision with argon was 50 eV and 70 eV. A mass range for themeasurement was m/z=100 to 1200.

FIGS. 18A and 18B show the results. FIG. 18A shows the results at thetime when the collision energy was 50 eV. FIG. 18B shows the results atthe time when the collision energy was 70 eV.

Example 3

This example will explain a light-emitting element (a light-emittingelement 1). In the light-emitting element, 4mDBTBPBfpm-II that is thecompound having the benzofuropyrimidine skeleton and described inEmbodiment 1 was used as a host material in a light-emitting layer thatcontained a phosphorescent substance emitting green.

The molecular structures of compounds used in this example are shown inStructural Formulae (i) to (v) and (100) below. The element structure inFIG. 1A was employed.

<<Fabrication of Light-Emitting Element 1>>

First, a glass substrate, over which a film of indium tin oxidecontaining silicon (ITSO) was formed to a thickness of 110 nm as thefirst electrode 101, was prepared. A surface of the ITSO film wascovered with a polyimide film so that an area of 2 mm×2 mm of thesurface was exposed. As pretreatment for forming the light-emittingelement over the substrate, the surface of the substrate was washed withwater and baked at 200° C. for 1 hour, and then UV-ozone treatment wasperformed for 370 seconds. After that, the substrate was transferredinto a vacuum evaporation apparatus where the pressure had been reducedto approximately 10⁻⁴ Pa, and was subjected to vacuum baking at 170° C.for 30 minutes in a heating chamber of the vacuum evaporation apparatus,and then the substrate was cooled down for about 30 minutes.

Then, the substrate was fixed to a holder provided in the vacuumevaporation apparatus so that the surface provided with ITSO faceddownward.

The pressure in the vacuum evaporation apparatus was reduced to 10⁻⁴ Pa.Then, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene)(abbreviation:DBT3P-II) represented by Structural Formula (i) andmolybdenum(VI) oxide were deposited by co-evaporation so that the weightratio of DBT3P-II to molybdenum oxide was 4:2, whereby thehole-injection layer 111 was formed. The thickness was set to 20 nm.Note that co-evaporation is an evaporation method in which a pluralityof different substances are concurrently vaporized from respectivedifferent evaporation sources.

Next, 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:BPAFLP) represented by Structural Formula (ii) was deposited byevaporation to a thickness of 20 nm, whereby the hole-transport layer112 was formed.

Then,4-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]benzofuro[3,2-d]pyrimidine(abbreviation: 4mDBTBPBfpm-II) represented by Structural Formula (100)and tris(2-phenylpyridinato-N,C^(2′))iridium(III) (abbreviation:[Ir(ppy)₃]) represented by Structural Formula (iii) were deposited byco-evaporation to a thickness of 20 nm on the hole-transport layer 112so that the weight ratio of 4mDBTBPBfpm-II to [Ir(ppy)₃] was 1:0.08, andthen, 4mDBTBPBfpm-II and [Ir(ppy)₃] were deposited by co-evaporation toa thickness of 20 nm so that the weight ratio of 4mDBTBPBfpm-II to[Ir(ppy)₃] was 1:0.04, whereby the light-emitting layer 113 was formed.

Next, 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II) represented by Structural Formula (iv) was deposited byevaporation to a thickness of 10 nm, and then bathophenanthroline(abbreviation: BPhen) represented by Structural Formula (v) wasdeposited by evaporation to a thickness of 15 nm, whereby theelectron-transport layer 114 was formed.

Then, lithium fluoride was deposited by evaporation to a thickness of 1nm on the electron-transport layer 114, whereby the electron-injectionlayer 115 was formed. Lastly, a film of aluminum was formed to athickness of 200 nm as the second electrode 102 which serves as acathode. Thus, the light-emitting element 1 was completed. Note that inall the above evaporation steps, evaporation was performed by aresistance-heating method.

<<Operation Characteristics of Light-Emitting Element 1>>

The light-emitting element 1 obtained as described above was sealed in aglove box containing a nitrogen atmosphere so as not to be exposed tothe air. Then, the operating characteristics of the light-emittingelement 1 were measured. Note that the measurement was carried out atroom temperature (in an atmosphere kept at 25° C.).

As to the light-emitting element 1, FIG. 19 shows the currentdensity-luminance characteristics, FIG. 20 shows the voltage-luminancecharacteristics, FIG. 21 shows the luminance-current efficiencycharacteristics, FIG. 22 shows the luminance-external quantum efficiencycharacteristics, and FIG. 23 shows the luminance-power efficiencycharacteristics.

FIG. 21 shows that the light-emitting element 1 has highluminance-current efficiency characteristics and thus has high emissionefficiency. Accordingly, 4mDBTBPBfpm-II, which is the compound havingthe benzofuropyrimidine skeleton and described in Embodiment 1, has ahigh triplet excitation level (T₁ level) and a wide energy gap, andallows even a phosphorescent substance emitting green to be effectivelyexcited. Moreover, FIG. 20 shows that the light-emitting element 1 hasfavorable voltage-luminance characteristics and thus has low drivingvoltage. This means that 4mDBTBPBfpm-II, which is the compound havingthe benzofuropyrimidine skeleton and described in Embodiment 1, has ahigh carrier-transport property. FIG. 19 and FIG. 22 also show that thelight-emitting element 1 has favorable current density-luminancecharacteristics and favorable luminance-external quantum efficiencycharacteristics. Accordingly, the light-emitting element 1 has extremelyhigh power efficiency as shown in FIG. 23 .

FIG. 24 shows an emission spectrum at the time when a current of 0.1 mAwas made to flow in the fabricated light-emitting element 1. Theemission intensity is shown as a value relative to the maximum emissionintensity assumed to be 1. FIG. 24 reveals that the light-emittingelement 1 emits green light originating from [Ir(ppy)₃] functioning asthe light-emitting substance.

FIG. 25 shows the results of a reliability test in which thelight-emitting element 1 was driven under conditions that the initialluminance was 5000 cd/m² and the current density was constant. FIG. 25shows a change in normalized luminance from an initial luminance of100%. The results show that a decrease in luminance over driving time ofthe light-emitting element 1 is small, and thus the light-emittingelement 1 has favorable reliability.

Example 4

This example will explain a light-emitting element (a light-emittingelement 2). In the light-emitting element, 4mDBTBPBfpm-II that is thecompound having the benzofuropyrimidine skeleton and described inEmbodiment 1 was used as a host material in a light-emitting layer thatcontained a phosphorescent substance emitting green.

The molecular structures of compounds used in this example are shown inStructural Formulae (i) to (iii), (v), (vi), and (100) below. Theelement structure in FIG. 1A was employed.

<<Fabrication of Light-Emitting Element 2>>

First, a glass substrate, over which a film of indium tin oxidecontaining silicon (ITSO) was formed to a thickness of 110 nm as thefirst electrode 101, was prepared. A surface of the ITSO film wascovered with a polyimide film so that an area of 2 mm×2 mm of thesurface was exposed. As pretreatment for forming the light-emittingelement over the substrate, the surface of the substrate was washed withwater and baked at 200° C. for 1 hour, and then UV-ozone treatment wasperformed for 370 seconds. After that, the substrate was transferredinto a vacuum evaporation apparatus where the pressure had been reducedto approximately 10⁻⁴ Pa, and was subjected to vacuum baking at 170° C.for 30 minutes in a heating chamber of the vacuum evaporation apparatus,and then the substrate was cooled down for about 30 minutes.

Then, the substrate was fixed to a holder provided in the vacuumevaporation apparatus so that the surface provided with ITSO faceddownward.

The pressure in the vacuum evaporation apparatus was reduced to 10⁻⁴ Pa.Then, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene)(abbreviation:DBT3P-II) represented by Structural Formula (i) andmolybdenum(VI) oxide were deposited by co-evaporation so that the weightratio of DBT3P-II to molybdenum oxide was 4:2, whereby thehole-injection layer 111 was formed. The thickness was set to 20 nm.Note that co-evaporation is an evaporation method in which a pluralityof different substances are concurrently vaporized from respectivedifferent evaporation sources.

Next, 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:BPAFLP) represented by Structural Formula (ii) was deposited byevaporation to a thickness of 20 nm, whereby the hole-transport layer112 was formed.

Moreover,4-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]benzofuro[3,2-d]pyrimidine(abbreviation: 4mDBTBPBfpm-II) represented by Structural Formula (100),N-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF) represented by Structural Formula (vi), andtris(2-phenylpyridinato-N,C^(2′))iridium(III) (abbreviation: [Ir(ppy)₃])represented by Structural Formula (iii) were deposited by co-evaporationto a thickness of 20 nm on the hole-transport layer 112 so that theweight ratio of 4mDBTBPBfpm-II to PCBBiF and [Ir(ppy)₃] was0.5:0.5:0.05, and then, 4mDBTBPBfpm-II, PCBBiF, and [Ir(ppy)₃] weredeposited by co-evaporation to a thickness of 20 nm so that the weightratio of 4mDBTBPBfpm-II to PCBBiF and [Ir(ppy)₃] was 0.8:0.2:0.05,whereby the light-emitting layer 113 was formed.

Next, 4mDBTBPBfpm-II was deposited by evaporation to a thickness of 10nm, and then bathophenanthroline (abbreviation: BPhen) represented byStructural Formula (v) was deposited by evaporation to a thickness of 15nm, whereby the electron-transport layer 114 was formed.

Then, lithium fluoride was deposited by evaporation to a thickness of 1nm on the electron-transport layer 114, whereby the electron-injectionlayer 115 was formed. Lastly, a film of aluminum was formed to athickness of 200 nm as the second electrode 102 which serves as acathode. Thus, the light-emitting element 2 was completed. Note that inall the above evaporation steps, evaporation was performed by aresistance-heating method.

<<Operation Characteristics of Light-Emitting Element 2>>

The light-emitting element 2 obtained as described above was sealed in aglove box containing a nitrogen atmosphere so as not to be exposed tothe air. Then, the operating characteristics of the light-emittingelement 2 were measured. Note that the measurement was carried out atroom temperature (in an atmosphere kept at 25° C.).

As to the light-emitting element 2, FIG. 26 shows the currentdensity-luminance characteristics, FIG. 27 shows the voltage-luminancecharacteristics, FIG. 28 shows the luminance-current efficiencycharacteristics, FIG. 29 shows the luminance-external quantum efficiencycharacteristics, and FIG. 30 shows the luminance-power efficiencycharacteristics.

FIG. 28 shows that the light-emitting element 2 has highluminance-current efficiency characteristics and thus has high emissionefficiency. Accordingly, 4mDBTBPBfpm-II, which is the compound havingthe benzofuropyrimidine skeleton and described in Embodiment 1, has ahigh triplet excitation level (T₁ level) and a wide energy gap, andallows even a phosphorescent substance emitting green to be effectivelyexcited. Moreover, FIG. 27 shows that the light-emitting element 2 hasfavorable voltage-luminance characteristics and thus has low drivingvoltage. This means that 4mDBTBPBfpm-II, which is the compound havingthe benzofuropyrimidine skeleton and described in Embodiment 1, has ahigh carrier-transport property. FIG. 26 and FIG. 29 also show that thelight-emitting element 2 has favorable current density-luminancecharacteristics and favorable luminance-external quantum efficiencycharacteristics. Accordingly, the light-emitting element 2 has extremelyhigh power efficiency as shown in FIG. 30 .

FIG. 31 shows an emission spectrum at the time when a current of 0.1 mAwas made to flow in the fabricated light-emitting element 2. Theemission intensity is shown as a value relative to the maximum emissionintensity assumed to be 1. FIG. 31 reveals that the light-emittingelement 2 emits green light originating from [Ir(ppy)₃] functioning asthe light-emitting substance.

FIG. 32 shows the results of a reliability test in which thelight-emitting element 2 was driven under conditions that the initialluminance was 5000 cd/m² and the current density was constant. FIG. 32shows a change in normalized luminance from an initial luminance of100%. The results show that a decrease in luminance over driving time ofthe light-emitting element 2 is small, and thus the light-emittingelement 2 has favorable reliability.

Example 5

In this example, a light-emitting element (a light-emitting element 3)will be described. In the light-emitting element, 4mDBTBPBfpm-II that isthe compound having the benzofuropyrimidine skeleton and described inEmbodiment 1 was used as a host material in a light-emitting layer thatcontained a phosphorescent substance emitting yellowish green.

The molecular structures of compounds used in this example are shown inStructural Formulae (i), (ii), (v) to (vii), and (100) below. Theelement structure in FIG. 1A was employed.

<<Fabrication of Light-Emitting Element 3>>

First, a glass substrate, over which a film of indium tin oxidecontaining silicon (ITSO) was formed to a thickness of 110 nm as thefirst electrode 101, was prepared. A surface of the ITSO film wascovered with a polyimide film so that an area of 2 mm×2 mm of thesurface was exposed. As pretreatment for forming the light-emittingelement over the substrate, the surface of the substrate was washed withwater and baked at 200° C. for 1 hour, and then UV-ozone treatment wasperformed for 370 seconds. After that, the substrate was transferredinto a vacuum evaporation apparatus where the pressure had been reducedto approximately 10⁻⁴ Pa, and was subjected to vacuum baking at 170° C.for 30 minutes in a heating chamber of the vacuum evaporation apparatus,and then the substrate was cooled down for about 30 minutes.

Then, the substrate was fixed to a holder provided in the vacuumevaporation apparatus so that the surface provided with ITSO faceddownward.

The pressure in the vacuum evaporation apparatus was reduced to 10⁻⁴ Pa.Then, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene)(abbreviation:DBT3P-II) represented by Structural Formula (i) andmolybdenum(VI) oxide were deposited by co-evaporation so that the weightratio of DBT3P-II to molybdenum oxide was 4:2, whereby thehole-injection layer 111 was formed. The thickness was set to 20 nm.Note that co-evaporation is an evaporation method in which a pluralityof different substances are concurrently vaporized from respectivedifferent evaporation sources.

Next, 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:BPAFLP) represented by Structural Formula (ii) was deposited byevaporation to a thickness of 20 nm, whereby the hole-transport layer112 was formed.

Moreover,4-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]benzofuro[3,2-d]pyrimidine(abbreviation: 4mDBTBPBfpm-II) represented by Structural Formula (100),N-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF) represented by Structural Formula (vi), andbis[2-(6-tert-butyl-4-pyrimidinyl-κN3)phenyl-κC](2,4-pentanedionato-κ²O,O′)iridium(III) (abbreviation: [Ir(tBuppm)₂(acac)]) represented by StructuralFormula (iii) were deposited by co-evaporation to a thickness of 20 nmon the hole-transport layer 112 so that the weight ratio of4mDBTBPBfpm-II to PCBBiF and [Ir(tBuppm)₂(acac)] was 0.5:0.5:0.05, andthen, 4mDBTBPBfpm-II, PCBBiF, and [Ir(tBuppm)₂(acac)] were deposited byco-evaporation to a thickness of 20 nm so that the weight ratio of4mDBTBPBfpm-II to PCBBiF and [Ir(tBuppm)₂(acac)] was 0.8:0.2:0.05,whereby the light-emitting layer 113 was formed.

Next, 4mDBTBPBfpm-II was deposited by evaporation to a thickness of 10nm, and then bathophenanthroline (abbreviation: BPhen) represented byStructural Formula (v) was deposited by evaporation to a thickness of 15nm, whereby the electron-transport layer 114 was formed.

Then, lithium fluoride was deposited by evaporation to a thickness of 1nm on the electron-transport layer 114, whereby the electron-injectionlayer 115 was formed. Lastly, a film of aluminum was formed to athickness of 200 nm as the second electrode 102 which serves as acathode. Thus, the light-emitting element 3 was completed. Note that inall the above evaporation steps, evaporation was performed by aresistance-heating method.

<<Operation Characteristics of Light-Emitting Element 3>>

The light-emitting element 3 obtained as described above was sealed in aglove box containing a nitrogen atmosphere so as not to be exposed tothe air. Then, the operating characteristics of the light-emittingelement 3 were measured. Note that the measurement was carried out atroom temperature (in an atmosphere kept at 25° C.).

As to the light-emitting element 3, FIG. 33 shows the currentdensity-luminance characteristics, FIG. 34 shows the voltage-luminancecharacteristics, FIG. 35 shows the luminance-current efficiencycharacteristics, FIG. 36 shows the luminance-external quantum efficiencycharacteristics, and FIG. 37 shows the luminance-power efficiencycharacteristics.

FIG. 35 shows that the light-emitting element 3 has highluminance-current efficiency characteristics and thus has high emissionefficiency. Accordingly, 4mDBTBPBfpm-II, which is the compound havingthe benzofuropyrimidine skeleton and described in Embodiment 1, has ahigh triplet excitation level (T₁ level) and a wide energy gap, andallows even a phosphorescent substance emitting yellowish green to beeffectively excited. Moreover, FIG. 34 shows that the light-emittingelement 3 has favorable voltage-luminance characteristics and thus haslow driving voltage. This means that 4mDBTBPBfpm-II, which is thecompound having the benzofuropyrimidine skeleton and described inEmbodiment 1, has a high carrier-transport property. FIG. 33 and FIG. 36also show that the light-emitting element 3 has extremely favorablecurrent density-luminance characteristics and favorableluminance-external quantum efficiency characteristics. Accordingly, thelight-emitting element 3 has extremely high power efficiency as shown inFIG. 37 .

FIG. 38 shows an emission spectrum at the time when a current of 0.1 mAwas made to flow in the fabricated light-emitting element 3. Theemission intensity is shown as a value relative to the maximum emissionintensity assumed to be 1. FIG. 38 reveals that the light-emittingelement 3 emits yellowish green light originating from[Ir(tBuppm)₂(acac)] functioning as the light-emitting substance.

FIG. 39 shows the results of a reliability test in which thelight-emitting element 3 was driven under conditions that the initialluminance was 5000 cd/m² and the current density was constant. FIG. 39shows a change in normalized luminance from an initial luminance of100%. The results show that a decrease in luminance over driving time ofthe light-emitting element 3 is small, and thus the light-emittingelement 3 has favorable reliability.

Example 6 Synthesis Example 3

In this synthesis example, a synthesis example of4-{3-[6-(9,9-dimethylfluoren-2-yl)dibenzothiophen-4-yl]phenyl}benzofuro[3,2-d]pyrimidine(abbreviation: 4mFDBtPBfpm) that is the compound having thebenzofuropyrimidine skeleton and represented by Structural Formula (115)in Embodiment 1 will be specifically described. The structural formulaof 4mFDBtPBfpm is shown below.

Step 1: Synthesis of 4-(9,9-Dimethylfluoren-2-yl)dibenzothiophene

First, 19 g of 2-bromo-9,9-dimethylfluorene, 16 g ofdibenzothiophen-4-ylboronic acid, 0.43 g oftris(2-methylphenyl)phosphine (abbreviation: P(o-tolyl)₃), 35 mL of a 2M aqueous solution of potassium carbonate, 270 mL of toluene, and 90 mLof ethanol were put in a three-neck flask equipped with a reflux pipe,and the air in the flask was replaced with nitrogen. Then, 0.16 g ofpalladium acetate was added, and heating was performed at 90° C. for 13hours. Further, 0.21 g of P(o-tolyl)₃ and 79 mg of palladium acetatewere added and heating was performed at 90° C. for 17 hours. Water wasadded into the resulting mixture, and extraction with toluene wasperformed. The solution of the extract was washed with water and asaturated aqueous solution of sodium chloride. Then, the solution wasdried over magnesium sulfate and the solution obtained by the drying wasfiltered. The solvent in the filtrate was distilled off, and theresulting residue was dissolved in toluene. The solution was subjectedto filtration through a filter aid in which Celite (Catalog No.531-16855, manufactured by Wako Pure Chemical Industries, Ltd. (the sameapplies to Celite in the following description)), alumina, and Florisil(Catalog No. 540-00135, manufactured by Wako Pure Chemical Industries,Ltd. (the same applies to Florisil in the following description)) werestacked in this order. The solvent was distilled off, and purificationwas performed by silica gel column chromatography using toluene andhexane in a volume ratio of 1:10 as a developing solvent. The solvent inthe resulting solution was distilled off and recrystallization wasperformed using a mixed solvent of toluene and hexane, so that a whitesolid was obtained in a yield of 70%. Synthesis Scheme (a-3) of Step 1is shown below.

Step 2: Synthesis of6-(9,9-Dimethylfluoren-2-yl)dibenzothiophen-4-ylboronic Acid

Next, 17 g of 4-(9,9-dimethylfluoren-2-yl)dibenzothiophene was put in athree-neck flask and the air in the flask was replaced with nitrogen.Then, 250 mL of tetrahydrofuran (dehydrated) was added, the flask wascooled down to −40° C. in a cryostat, and 34 mL of a 1.6 M hexanesolution of n-butyl lithium was dropped, which was followed by stirringat room temperature for 1 hour. The flask was cooled down to −40° C.Then, 6.6 mL of trimethyl borate was dropped, the temperature was raisedto room temperature, and stirring was performed for 21 hours with thetemperature maintained. Then, 50 mL of 1 M hydrochloric acid was addedand stirring was performed for 1 hour. The resulting mixture wassubjected to extraction with ethyl acetate, washing using a saturatedaqueous solution of sodium hydrogen carbonate and washing using asaturated aqueous solution of sodium chloride were performed, andmagnesium sulfate was added, which was followed by filtration. Thesolvent in the filtrate was distilled off. Toluene was added and washingusing ultrasonic waves was performed. Suction filtration was performedto give a yellowish white solid in a yield of 34%. Synthesis Scheme(b-3) of Step 2 is shown below.

Step 3: Synthesis of4-(3-Bromophenyl)-6-(9,9-dimethylfluoren-2-yl)dibenzothiophene

Next, 7.1 g of 6-(9,9-dimethylfluoren-2-yl)dibenzothiophen-4-ylboronicacid, 5.2 g of 3-iodo-bromobenzene, 0.57 g of P(o-tolyl)₃, 5.1 g ofpotassium carbonate, 74 mL of toluene, 19 mL of ethanol, and 19 mL ofwater were put in a three-neck flask equipped with a reflux pipe, andthe air in the flask was replaced with nitrogen. Then, 0.21 g ofpalladium acetate was added and heating was performed at 80° C. for 8hours. The resulting mixture was subjected to extraction with toluene,washing using a saturated aqueous solution of sodium chloride wasperformed. Then, the solution was dried over magnesium sulfate and thesolution obtained by the drying was filtered. The solvent in thisfiltrate was distilled off, and the resulting residue was dissolved intoluene. The solution was subjected to filtration through a filter aidin which Celite, alumina, and Florisil were stacked in this order. Thesolvent was distilled off, and purification was performed by silica gelcolumn chromatography using toluene and hexane in a volume ratio of 1:10as a developing solvent, whereby a yellowish white solid was obtained ina yield of 74%. Synthesis Scheme (c-3) of Step 3 is shown below.

Step 4: Synthesis of3-[6-(9,9-Dimethylfluoren-2-yl)dibenzothiophen-4-yl]phenylboronic AcidPinacol Ester

Next, 2.5 g of4-(3-bromophenyl)-6-(9,9-dimethylfluoren-2-yl)dibenzothiophene, 1.2 g ofbis(pinacol)diboron, and 1.4 g of potassium acetate were put in athree-neck flask equipped with a reflux pipe, and the air in the flaskwas replaced with nitrogen. Then, 300 mL of dioxane and 0.19 g of[1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloromethaneadduct (abbreviation: Pd(dppf)Cl₂) were added and heating was performedat 90° C. for 9.5 hours. Water was added to the resulting mixture andthe solution was subjected to extraction with ethyl acetate. Washingusing a saturated aqueous solution of sodium chloride was performed.Then, the solution was dried over magnesium sulfate and the solutionobtained by the drying was filtered. The solvent in this filtrate wasdistilled off, and the resulting residue was dissolved in toluene. Thesolution was subjected to filtration through a filter aid in whichCelite, alumina, and Florisil were stacked in this order. The solventwas distilled off, and purification was performed by flash columnchromatography using toluene and hexane in a volume ratio of 1:10 as adeveloping solvent, whereby a colorless oily substance was obtained in ayield of 17%. Synthesis Scheme (d-3) of Step 4 is shown below.

Step 5: Synthesis of 4mFDBtPBfpm

Lastly, 0.45 g of3-[6-(9,9-dimethylfluoren-2-yl)dibenzothiophen-4-yl]phenylboronic acidpinacol ester, 0.14 g of 4-chlorobenzofuro[3,2-d]pyrimidine, 0.45 g ofpotassium phosphate, 4 mL of dioxane, and 0.16 g of t-butanol were putin a three-neck flask, and the air in the flask was replaced withnitrogen; then, 1.8 mg of palladium acetate and 5.6 mg ofdi(1-adamantyl)-n-butylphosphine were added, and the mixture wasrefluxed to promote a reaction. Water was added to the resulting mixtureand the solution was subjected to extraction with ethyl acetate. Washingusing a saturated aqueous solution of sodium chloride was performed, andmagnesium sulfate was added, which was followed by gravity filtration.The solvent in the filtrate was distilled off, and purification wasperformed by flash column chromatography using toluene and hexane in avolume ratio of 1:5 as a developing solvent, whereby a yellow solid wasobtained in a yield of 10%. Synthesis Scheme (e-3) of Step 5 is shownbelow.

Analysis results by nuclear magnetic resonance (¹H-NMR) spectroscopy ofthe yellow solid obtained in Step 3 are described below.

¹H-NMR. δ(CDCl₃): 1.37 (s, 6H), 7.28-7.31 (dt, 2H), 7.37 (d, 1H),7.44-7.50 (m, 2H), 7.58-7.66 (m, 5H), 7.69-7.73 (m, 3H), 7.75-7.78 (t,1H), 7.82 (s, 1H), 7.93 (d, 1H), 8.23-8.28 (m, 3H), 8.64 (td, 1H), 9.02(ts, 1H), 9.27 (s, 1H).

FIGS. 40A and 40B are ¹H NMR charts. Note that FIG. 40B shows anenlarged part of FIG. 40A in the range of 7.0 ppm to 9.5 ppm. Themeasurement results reveal that 4mFDBtPBfpm, which was the targetsubstance, was obtained.

Reference Example 1

In this reference example, a method for synthesizing4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II) used in Example 3 will be described.

Synthesis of 4,6-Bis[3-(4-dibenzothienyl)phenyl]pyrimidine(abbreviation: 4,6mDBTP2Pm-II)

Into a 100-mL recovery flask were put 1.0 g (6.7 mmol) of4,6-dichloropyrimidine, 5.1 g (17 mmol) of3-(dibenzothiophen-4-yl)phenylboronic acid, 3.5 g (34 mmol) of sodiumcarbonate, 20 mL of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone(abbreviation: DMPU), and 10 mL of water. This mixture was degassed bybeing stirred while the pressure was reduced. To this mixture was added56 mg (81 μmol) of bis(triphenylphosphine)palladium(II) dichloride, andthe atmosphere was replaced with argon. The mixture was stirred whilethe reaction container was heated by irradiation with microwaves (2.45GHz, 100 W) for 1.5 hours. After the heating, water was added to themixture, and the mixture was filtered to give a residue. The obtainedsolid was washed with dichloromethane and ethanol. To the obtained solidwas added toluene, and the mixture was subjected to suction filtrationthrough Celite, alumina, and Florisil. The filtrate was concentrated togive a solid. The obtained solid was recrystallized from toluene to give2.52 g of a white solid in a yield of 63%. A synthesis scheme involvingthe above reaction is shown below.

By a train sublimation method, 2.50 g of the obtained solid was purifiedby sublimation. The purification by sublimation was performed by heatingat 300° C. under a pressure of 3.6 Pa with a flow rate of argon gas of 5mL/min. After the purification by sublimation, 1.98 g of a white solidwas obtained at a collection rate of 790%.

This compound was identified as4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II), which was an objective substance, by a nuclear magneticresonance (1H-NMR) method.

¹H-NMR data of the obtained substance are as follows: ¹H NMR (CDCl₃, 300MHz): δ=7.41-7.51 (m, 4H), 7.58-7.62 (m, 4H), 7.68-7.79 (m, 4H), 8.73(dt, J1=8.4 Hz, J2=0.9 Hz, 2H), 8.18-8.27 (m, 7H), 8.54 (t, J1=1.5 Hz,2H), 9.39 (d, J1=0.9 Hz, 1H).

Reference Example 2

In this reference example, a method for synthesizingN-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF) used in Examples 4 and 5 will be described.

Step 1: Synthesis ofN-(1,1′-Biphenyl-4-yl)-9,9-dimethyl-N-phenyl-9H-fluoren-2-amine

In a 1-L three-neck flask were placed 45 g (0.13 mol) ofN-(1,1′-biphenyl-4-yl)-9,9-dimethyl-9H-fluoren-2-amine, 36 g (0.38 mol)of sodium tert-butoxide, 21 g (0.13 mol) of bromobenzene, and 500 mL oftoluene. The mixture was degassed by being stirred while the pressurewas being reduced, and after the degassing, the atmosphere in the flaskwas replaced with nitrogen. Then, 0.8 g (1.4 mmol) ofbis(dibenzylideneacetone)palladium(0) and 12 mL (5.9 mmol) oftri(tert-butyl)phosphine (a 10 wt % hexane solution) were added. Asynthesis scheme of Step 1 is shown below.

The mixture was stirred at 90° C. under a nitrogen stream for 2 hours.Then, the mixture was cooled to room temperature, and a solid wasseparated by suction filtration. The obtained filtrate was concentratedto give about 200 mL of a brown liquid. The brown liquid was mixed withtoluene, and the resulting solution was purified using Celite, alumina,and Florisil. The resulting filtrate was concentrated to give a lightyellow liquid. The light yellow liquid was recrystallized from hexane togive 52 g of target light yellow powder in a yield of 95%.

Step 2: Synthesis ofN-(1,1′-Biphenyl-4-yl)-N-(4-bromophenyl)-9,9-dimethyl-9H-fluoren-2-amine

In a 1-L Erlenmeyer flask was placed 45 g (0.10 mol) ofN-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-phenyl-9H-fluoren-2-amine, whichwas dissolved in 225 mL of toluene by stirring while being heated. Afterthe solution was naturally cooled to room temperature, 225 mL of ethylacetate and 18 g (0.10 mol) of N-bromosuccinimide (abbreviation: NBS)were added, and the mixture was stirred at room temperature for 2.5hours. After the stirring, the mixture was washed three times with asaturated aqueous solution of sodium hydrogen carbonate and once with asaturated aqueous solution of sodium chloride. Magnesium sulfate wasadded to the resulting organic layer, and the mixture was left still for2 hours for drying. The mixture was subjected to gravity filtration toremove magnesium sulfate, and the resulting filtrate was concentrated togive a yellow liquid. The yellow liquid was mixed with toluene, and thesolution was purified using Celite, alumina, and Florisil. The resultingsolution was concentrated to give a light yellow solid. The light yellowsolid was recrystallized from toluene/ethanol to give 47 g of targetwhite powder in a yield of 89%. A synthesis scheme of Step 2 is shownbelow.

Step 3: Synthesis of PCBBiF

In a 1-L three-neck flask were placed 41 g (80 mmol) ofN-(1,1′-biphenyl-4-yl)-N-(4-bromophenyl)-9,9-dimethyl-9H-fluoren-2-amineand 25 g (88 mmol) of 9-phenyl-9H-carbazol-3-ylboronic acid, to which240 mL of toluene, 80 mL of ethanol, and 120 mL of an aqueous solutionof potassium carbonate (2.0 mol/L) were added. The mixture was degassedby being stirred while the pressure was being reduced, and after thedegassing, the atmosphere in the flask was replaced with nitrogen.Further, 27 mg (0.12 mmol) of palladium(II) acetate and 154 mg (0.5mmol) of tri(ortho-tolyl)phosphine were added. The mixture was degassedagain by being stirred while the pressure was being reduced, and afterthe degassing, the atmosphere in the flask was replaced with nitrogen.The mixture was stirred at 110° C. under a nitrogen stream for 1.5hours. A synthesis scheme of Step 3 is shown below.

After the mixture was naturally cooled to room temperature while beingstirred, the aqueous layer of the mixture was extracted twice withtoluene. The resulting solution of the extract and the organic layerwere combined and washed twice with water and twice with a saturatedaqueous solution of sodium chloride. Magnesium sulfate was added to thesolution, and the mixture was left still for drying. The mixture wassubjected to gravity filtration to remove magnesium sulfate, and theresulting filtrate was concentrated to give a brown solution. The brownsolution was mixed with toluene, and the resulting solution was purifiedusing Celite, alumina, and Florisil. The resulting filtrate wasconcentrated to give a light yellow solid. The light yellow solid wasrecrystallized from ethyl acetate/ethanol to give 46 g of target lightyellow powder in a yield of 88%.

By a train sublimation method, 38 g of the obtained light yellow powderwas purified by sublimation. In the sublimation purification, the lightyellow powder was heated at 345° C. under a pressure of 3.7 Pa with anargon flow rate of 15 mL/min. After the sublimation purification, 31 gof a target light yellow solid was obtained at a collection rate of 83%.

This compound was identified asN-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF), which was the target of the synthesis, bynuclear magnetic resonance (NMR) spectroscopy.

¹H-NMR data of the obtained light yellow solid are as follows: ¹H-NMR(CDCl₃, 500 MHz): δ=1.45 (s, 6H), 7.18 (d, J=8.0 Hz, 1H), 7.27-7.32 (m,8H), 7.40-7.50 (m, 7H), 7.52-7.53 (m, 2H), 7.59-7.68 (m, 12H), 8.19 (d,J=8.0 Hz, 1H), 8.36 (d, J=1.1 Hz, 1H).

REFERENCE NUMERALS

101: first electrode, 102: second electrode, 103: EL layer, 111:hole-injection layer, 112: hole-transport layer, 113: light-emittinglayer, 114: electron-transport layer, 501: first electrode, 502: secondelectrode, 511: first light-emitting unit, 512: second light-emittingunit, 513: charge generation layer, 601: driver circuit portion (sourceside driver circuit), 602: pixel portion, 603: driver circuit portion(gate side driver circuit), 604: sealing substrate, 605: sealingmaterial, 607: space, 608: wiring, 609: FPC (flexible printed circuit),610: element substrate, 611: switching TFT, 612: current controllingTFT, 613: first electrode, 614: insulator, 616: EL layer, 617: secondelectrode, 618: light-emitting element, 623: n-channel TFT, 624:p-channel TFT, 901: housing, 902: liquid crystal layer, 903: backlight,904: housing, 905: driver IC, 906: terminal, 951: substrate, 952:electrode, 953: insulating layer, 954: partition layer, 955: EL layer,956: electrode, 1001: substrate, 1002: base insulating film, 1003: gateinsulating film, 1006: gate electrode, 1007: gate electrode, 1008: gateelectrode, 1020: first interlayer insulating film, 1021: secondinterlayer insulating film, 1022: electrode, 1024W: first electrode of alight-emitting element, 1024R: first electrode of a light-emittingelement, 1024G: first electrode of a light-emitting element, 1024B:first electrode of a light-emitting element, 1025: partition wall, 1028:EL layer, 1029: second electrode of a light-emitting element, 1031:sealing substrate, 1032: sealant, 1033: transparent base material,1034R: red coloring layer, 1034G: green coloring layer, 1034B: bluecoloring layer, 1035: black layer (black matrix), 1037: third interlayerinsulating film, 1040: pixel portion, 1041: driver circuit portion,1042: peripheral portion, 1201: source electrode, 1202: active layer,1203: drain electrode, 1204: gate electrode, 2001: housing, 2002: lightsource, 3001: lighting device, 5000: display region, 5001: displayregion, 5002: display region, 5003: display region, 5004: displayregion, 5005: display region, 7101: housing, 7103: display portion,7105: stand, 7107: display portion, 7109: operation key, 7110: remotecontroller, 7201: main body, 7202: housing, 7203: display portion, 7204:keyboard, 7205: external connection port, 7206: pointing device, 7301:housing, 7302: housing, 7303: joint portion, 7304: display portion,7305: display portion, 7306: speaker portion, 7307: recording mediuminsertion portion, 7308: LED lamp, 7309: operation key, 7310: connectionterminal, 7311: sensor, 7401: housing, 7402: display portion, 7403:operation button, 7404: external connection port, 7405: speaker, 7406:microphone, 9630: housing, 9631: display portion, 9631 a: displayportion, 9631 b: display portion, 9632 a: touchscreen region, 9632 b:touchscreen region, 9633: solar cell, 9634: charge and discharge controlcircuit, 9635: battery, 9636: DC-to-DC converter, 9637: operation key,9638: converter, 9639: keyboard display switching button, 9033: clasp,9034: display mode switch, 9035: power switch, 9036: power-savingswitch, and 9038: operation switch

This application is based on Japanese Patent Application serial no.2013-064261 filed with Japan Patent Office on Mar. 26, 2013, the entirecontents of which are hereby incorporated by reference.

The invention claimed is:
 1. A material for a light-emitting layer of alight-emitting element comprising: a first compound; and a secondcompound, wherein the first compound is represented by formula (G1):

wherein A¹ represents a group having 6 to 100 carbon atoms, the groupcomprising at least one of a phenyl group, a fluorenyl group, aphenanthryl group, a triphenylenyl group, a dibenzothiophenyl group, adibenzofuranyl group, a carbazolyl group, a benzimidazolyl group, abenzoxazolyl group, a benzthiazolyl group, and a triphenyl amineskeleton, and wherein R¹ to R⁵ separately represent any one of hydrogen,an alkyl group having 1 to 6 carbon atoms, a substituted orunsubstituted monocyclic saturated hydrocarbon having 5 to 7 carbonatoms, a substituted or unsubstituted polycyclic saturated hydrocarbonhaving 7 to 10 carbon atoms, and a substituted or unsubstituted arylgroup having 6 to 13 carbon atoms.
 2. A material for a light-emittinglayer of a light-emitting element comprising: a first compound; and asecond compound, wherein the first compound is represented by formula(G1):

wherein A¹ represents a group having 6 to 100 carbon atoms, the groupcomprising at least one of a phenyl group, a fluorenyl group, aphenanthryl group, a triphenylenyl group, a dibenzothiophenyl group, adibenzofuranyl group, a carbazolyl group, a benzimidazolyl group, abenzoxazolyl group, a benzthiazolyl group, and a triphenyl amineskeleton, wherein R¹ to R⁵ separately represent any one of hydrogen, analkyl group having 1 to 6 carbon atoms, a substituted or unsubstitutedmonocyclic saturated hydrocarbon having 5 to 7 carbon atoms, asubstituted or unsubstituted polycyclic saturated hydrocarbon having 7to 10 carbon atoms, and a substituted or unsubstituted aryl group having6 to 13 carbon atoms, and wherein an emission spectrum of the materialis on the longer wavelength side than each of an emission spectrum ofthe first compound and an emission spectrum of the second compound. 3.The material for a light-emitting layer of a light-emitting element,according to claim 1, wherein the first compound and the second compoundform an exciplex in the light-emitting layer.
 4. The material for alight-emitting layer of a light-emitting element, according to claim 1,wherein the first compound is represented by formula (G2):

wherein Ht_(uni) represents any one of a substituted or unsubstituteddibenzothiophenyl group, a substituted or unsubstituted dibenzofuranylgroup, a substituted or unsubstituted carbazolyl group; wherein αrepresents a substituted or unsubstituted phenylene group; wherein n isan integer from 0 to 4; and wherein R¹ to R⁵ separately represent anyone of hydrogen, an alkyl group having 1 to 6 carbon atoms, asubstituted or unsubstituted monocyclic saturated hydrocarbon having 5to 7 carbon atoms, a substituted or unsubstituted polycyclic saturatedhydrocarbon having 7 to 10 carbon atoms, and a substituted orunsubstituted aryl group having 6 to 13 carbon atoms.
 5. The materialfor a light-emitting layer of a light-emitting element, according toclaim 1, wherein the n is
 2. 6. The material for a light-emitting layerof a light-emitting element, according to claim 1, wherein the firstcompound is represented by formula (G3):

wherein Ht_(uni) represents any one of a substituted or unsubstituteddibenzothiophenyl group, a substituted or unsubstituted dibenzofuranylgroup, a substituted or unsubstituted carbazolyl group; and wherein R¹to R⁵ separately represent any one of hydrogen, an alkyl group having 1to 6 carbon atoms, a substituted or unsubstituted monocyclic saturatedhydrocarbon having 5 to 7 carbon atoms, a substituted or unsubstitutedpolycyclic saturated hydrocarbon having 7 to 10 carbon atoms, and asubstituted or unsubstituted aryl group having 6 to 13 carbon atoms. 7.The material for a light-emitting layer of a light-emitting element,according to claim 6, wherein Ht_(uni) represents any one of groupsrepresented by formulae (Ht-1) to (Ht-6):

R⁶ to R¹⁵ separately represent any one of hydrogen, an alkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted phenylgroup; and R¹⁶ represents any one of an alkyl group having 1 to 6 carbonatoms and a substituted or unsubstituted phenyl group.
 8. The materialfor a light-emitting layer of a light-emitting element, according toclaim 1, wherein the first compound is represented by any one offormulae (100), (115), (200), and (300):


9. The material for a light-emitting layer of a light-emitting element,according to claim 1, wherein the second compound has an hole-transportproperty.
 10. The material for a light-emitting layer of alight-emitting element, according to claim 1, wherein the secondcompound is any one of a compound comprising a phenylamine skeleton, acompound comprising a carbazole skeleton, a compound comprising athiophene skeleton, and a compound comprising a furan skeleton.
 11. Thematerial for a light-emitting layer of a light-emitting element,according to claim 2, wherein the first compound and the second compoundform an exciplex in the light-emitting layer.
 12. The material for alight-emitting layer of a light-emitting element, according to claim 2,wherein the first compound is represented by formula (G2):

wherein Ht_(uni) represents any one of a substituted or unsubstituteddibenzothiophenyl group, a substituted or unsubstituted dibenzofuranylgroup, a substituted or unsubstituted carbazolyl group; wherein αrepresents a substituted or unsubstituted phenylene group; wherein n isan integer from 0 to 4; and wherein R¹ to R⁵ separately represent anyone of hydrogen, an alkyl group having 1 to 6 carbon atoms, asubstituted or unsubstituted monocyclic saturated hydrocarbon having 5to 7 carbon atoms, a substituted or unsubstituted polycyclic saturatedhydrocarbon having 7 to 10 carbon atoms, and a substituted orunsubstituted aryl group having 6 to 13 carbon atoms.
 13. The materialfor a light-emitting layer of a light-emitting element, according toclaim 2, wherein the n is
 2. 14. The material for a light-emitting layerof a light-emitting element, according to claim 2, wherein the firstcompound is represented by formula (G3):

wherein Ht_(uni) represents any one of a substituted or unsubstituteddibenzothiophenyl group, a substituted or unsubstituted dibenzofuranylgroup, a substituted or unsubstituted carbazolyl group; and wherein R¹to R⁵ separately represent any one of hydrogen, an alkyl group having 1to 6 carbon atoms, a substituted or unsubstituted monocyclic saturatedhydrocarbon having 5 to 7 carbon atoms, a substituted or unsubstitutedpolycyclic saturated hydrocarbon having 7 to 10 carbon atoms, and asubstituted or unsubstituted aryl group having 6 to 13 carbon atoms. 15.The material for a light-emitting layer of a light-emitting element,according to claim 14, wherein Ht_(uni) represents any one of groupsrepresented by formulae (Ht-1) to (Ht-6):

R⁶ to R¹⁵ separately represent any one of hydrogen, an alkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted phenylgroup; and R¹⁶ represents any one of an alkyl group having 1 to 6 carbonatoms and a substituted or unsubstituted phenyl group.
 16. The materialfor a light-emitting layer of a light-emitting element, according toclaim 2, wherein the first compound is represented by any one offormulae (100), (115), (200), and (300):


17. The material for a light-emitting layer of a light-emitting element,according to claim 2, wherein the second compound has an hole-transportproperty.
 18. The material for a light-emitting layer of alight-emitting element, according to claim 2, wherein the secondcompound is any one of a compound comprising a phenylamine skeleton, acompound comprising a carbazole skeleton, a compound comprising athiophene skeleton, and a compound comprising a furan skeleton.